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usr/share/doc/alt-curlssl11/FEATURES.md 0000644 00000013551 15233257615 0013411 0 ustar 00 <!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. SPDX-License-Identifier: curl --> # Features -- what curl can do ## curl tool - config file support - multiple URLs in a single command line - range "globbing" support: [0-13], {one,two,three} - multiple file upload on a single command line - redirect stderr - parallel transfers ## libcurl - URL RFC 3986 syntax - custom maximum download time - custom lowest download speed acceptable - custom output result after completion - guesses protocol from hostname unless specified - supports .netrc - progress bar with time statistics while downloading - standard proxy environment variables support - have run on 101 operating systems and 28 CPU architectures - selectable network interface for outgoing traffic - IPv6 support on Unix and Windows - happy eyeballs dual-stack IPv4 + IPv6 connects - persistent connections - SOCKS 4 + 5 support, with or without local name resolving - *pre-proxy* support, for *proxy chaining* - supports username and password in proxy environment variables - operations through HTTP proxy "tunnel" (using CONNECT) - replaceable memory functions (malloc, free, realloc, etc) - asynchronous name resolving - both a push and a pull style interface - international domain names (IDN) - transfer rate limiting - stable API and ABI - TCP keep alive - TCP Fast Open - DNS cache (that can be shared between transfers) - non-blocking single-threaded parallel transfers - Unix domain sockets to server or proxy - DNS-over-HTTPS - uses non-blocking name resolves - selectable name resolver backend ## URL API - parses RFC 3986 URLs - generates URLs from individual components - manages "redirects" ## Header API - easy access to HTTP response headers, from all contexts - named headers - iterate over headers ## TLS - selectable TLS backend(s) - TLS False Start - TLS version control - TLS session resumption - key pinning - mutual authentication - Use dedicated CA cert bundle - Use OS-provided CA store - separate TLS options for HTTPS proxy ## HTTP - HTTP/0.9 responses are optionally accepted - HTTP/1.0 - HTTP/1.1 - HTTP/2, including multiplexing and server push - GET - PUT - HEAD - POST - multipart formpost (RFC 1867-style) - authentication: Basic, Digest, NTLM (9) and Negotiate (SPNEGO) to server and proxy - resume transfers - follow redirects - maximum amount of redirects to follow - custom HTTP request - cookie get/send fully parsed - reads/writes the Netscape cookie file format - custom headers (replace/remove internally generated headers) - custom user-agent string - custom referrer string - range - proxy authentication - time conditions - via HTTP proxy, HTTPS proxy or SOCKS proxy - HTTP/2 or HTTP/1.1 to HTTPS proxy - retrieve file modification date - Content-Encoding support for deflate, gzip, brotli and zstd - "Transfer-Encoding: chunked" support in uploads - HSTS - alt-svc - ETags - HTTP/1.1 trailers, both sending and getting ## HTTPS - HTTP/3 - using client certificates - verify server certificate - via HTTP proxy, HTTPS proxy or SOCKS proxy - select desired encryption - select usage of a specific TLS version - ECH ## FTP - download - authentication - Kerberos 5 - active/passive using PORT, EPRT, PASV or EPSV - single file size information (compare to HTTP HEAD) - 'type=' URL support - directory listing - directory listing names-only - upload - upload append - upload via http-proxy as HTTP PUT - download resume - upload resume - custom ftp commands (before and/or after the transfer) - simple "range" support - via HTTP proxy, HTTPS proxy or SOCKS proxy - all operations can be tunneled through proxy - customizable to retrieve file modification date - no directory depth limit ## FTPS - implicit `ftps://` support that use SSL on both connections - explicit "AUTH TLS" and "AUTH SSL" usage to "upgrade" plain `ftp://` connection to use SSL for both or one of the connections ## SSH (both SCP and SFTP) - selectable SSH backend - known hosts support - public key fingerprinting - both password and public key auth ## SFTP - both password and public key auth - with custom commands sent before/after the transfer - directory listing ## TFTP - download - upload ## TELNET - connection negotiation - custom telnet options - stdin/stdout I/O ## LDAP - full LDAP URL support ## DICT - extended DICT URL support ## FILE - URL support - upload - resume ## SMB - SMBv1 over TCP and SSL - download - upload - authentication with NTLMv1 ## SMTP - authentication: Plain, Login, CRAM-MD5, Digest-MD5, NTLM, Kerberos 5 and External - send emails - mail from support - mail size support - mail auth support for trusted server-to-server relaying - multiple recipients - via http-proxy ## SMTPS - implicit `smtps://` support - explicit "STARTTLS" usage to "upgrade" plain `smtp://` connections to use SSL - via http-proxy ## POP3 - authentication: Clear Text, APOP and SASL - SASL based authentication: Plain, Login, CRAM-MD5, Digest-MD5, NTLM, Kerberos 5 and External - list emails - retrieve emails - enhanced command support for: CAPA, DELE, TOP, STAT, UIDL and NOOP via custom requests - via http-proxy ## POP3S - implicit `pop3s://` support - explicit `STLS` usage to "upgrade" plain `pop3://` connections to use SSL - via http-proxy ## IMAP - authentication: Clear Text and SASL - SASL based authentication: Plain, Login, CRAM-MD5, Digest-MD5, NTLM, Kerberos 5 and External - list the folders of a mailbox - select a mailbox with support for verifying the `UIDVALIDITY` - fetch emails with support for specifying the UID and SECTION - upload emails via the append command - enhanced command support for: EXAMINE, CREATE, DELETE, RENAME, STATUS, STORE, COPY and UID via custom requests - via http-proxy ## IMAPS - implicit `imaps://` support - explicit "STARTTLS" usage to "upgrade" plain `imap://` connections to use SSL - via http-proxy ## MQTT - Subscribe to and publish topics using URL scheme `mqtt://broker/topic` usr/share/doc/alt-curlssl11/FAQ.md 0000644 00000164724 15233257616 0012614 0 ustar 00 <!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. SPDX-License-Identifier: curl --> # Frequently Asked Questions # Philosophy ## What is curl? curl is the name of the project. The name is a play on *Client for URLs*, originally with URL spelled in uppercase to make it obvious it deals with URLs. The fact it can also be read as *see URL* also helped, it works as an abbreviation for *Client URL Request Library* or why not the recursive version: *curl URL Request Library*. The curl project produces two products: ### libcurl A client-side URL transfer library, supporting DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, MQTTS, POP3, POP3S, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS and WSS. libcurl supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading, Kerberos, SPNEGO, HTTP form based upload, proxies, cookies, user+password authentication, file transfer resume, http proxy tunneling and more. libcurl is highly portable, it builds and works identically on numerous platforms. The [internals document](https://curl.se/docs/install.html#Ports) lists more than 110 operating systems and 28 CPU architectures on which curl has been reported to run. libcurl is free, thread-safe, IPv6 compatible, feature-rich, well supported and fast. ### curl A command line tool for getting or sending data using URL syntax. Since curl uses libcurl, curl supports the same wide range of common Internet protocols that libcurl does. We pronounce curl with an initial k sound. It rhymes with words like girl and earl. [This is a short WAV file](https://media.merriam-webster.com/soundc11/c/curl0001.wav) to help you. There are numerous sub-projects and related projects that also use the word curl in the project names in various combinations, but you should take notice that this FAQ is directed at the command-line tool named curl (and libcurl the library), and may therefore not be valid for other curl-related projects. (There is however a small section for the PHP/CURL in this FAQ.) ## What is libcurl? libcurl is a reliable and portable library for doing Internet data transfers using one or more of its supported Internet protocols. You can use libcurl freely in your application, be it open source, commercial or closed-source. libcurl is most probably the most portable, most powerful and most often used C-based multi-platform file transfer library on this planet - be it open source or commercial. ## What is curl not? curl is not a Wget clone. That is a common misconception. Never, during curl's development, have we intended curl to replace Wget or compete on its market. curl is targeted at single-shot file transfers. curl is not a website mirroring program. If you want to use curl to mirror something: fine, go ahead and write a script that wraps around curl or use libcurl to make it reality. curl is not an FTP site mirroring program. Sure, get and send FTP with curl but if you want systematic and sequential behavior you should write a script (or write a new program that interfaces libcurl) and do it. curl is not a PHP tool, even though it works perfectly well when used from or with PHP (when using the PHP/CURL module). curl is not a program for a single operating system. curl exists, compiles, builds and runs under a wide range of operating systems, including all modern Unixes (and a bunch of older ones too), Windows, Amiga, OS/2, macOS, QNX etc. ## When would you make curl do ... ? We love suggestions of what to change in order to make curl and libcurl better. We do however believe in a few rules when it comes to the future of curl: curl the command line tool is to remain a non-graphical command line tool. If you want GUIs or fancy scripting capabilities, you should look for another tool that uses libcurl. We do not add things to curl that other small and available tools already do well at the side. curl's output can be piped into another program or redirected to another file for the next program to interpret. We focus on protocol related issues and improvements. If you want to do more with the supported protocols than curl currently does, chances are good we would agree. If you want to add more protocols, we may agree. If you want someone else to do all the work while you wait for us to implement it for you, that is not a friendly attitude. We spend a considerable time already on maintaining and developing curl. In order to get more out of us, you should consider trading in some of your time and effort in return. Go to the [GitHub repository](https://github.com/curl/curl), fork the project, and create pull requests with your proposed changes. If you write the code, chances are better that it gets into curl faster. ## Who makes curl? curl and libcurl are not made by any single individual. Daniel Stenberg is project leader and main developer, but other persons' submissions are important and crucial. Anyone can contribute and post their changes and improvements and have them inserted in the main sources (of course on the condition that developers agree that the fixes are good). The full list of all contributors is found in the [docs/THANKS](https://curl.se/docs/thanks.html) file. curl is developed by a community, with Daniel at the wheel. ## What do you get for making curl? Project curl is entirely free and open. We do this voluntarily, mostly in our spare time. Companies may pay individual developers to work on curl. This is not controlled by nor supervised in any way by the curl project. We get help from companies. Haxx provides website, bandwidth, mailing lists etc, GitHub hosts [the primary git repository](https://github.com/curl/curl) and other services like the bug tracker. Also again, some companies have sponsored certain parts of the development in the past and I hope some continue to do so in the future. If you want to [support our project](https://curl.se/sponsors.html), consider a donation or a banner-program or even better: by helping us with coding, documenting or testing etc. ## What about CURL from curl.com? During the summer of 2001, curl.com was busy advertising their client-side programming language for the web, named CURL. We are in no way associated with curl.com or their CURL programming language. Our project name curl has been in effective use since 1998. We were not the first computer related project to use the name *curl* and do not claim any rights to the name. We recognize that we are living in parallel with curl.com and wish them every success. ## I have a problem, who do I mail? Please do not mail any single individual unless you really need to. Keep curl-related questions on a suitable mailing list. All available mailing lists are listed [online](https://curl.se/mail/). Keeping curl-related questions and discussions on mailing lists allows others to join in and help, to share their ideas, to contribute their suggestions and to spread their wisdom. Keeping discussions on public mailing lists also allows for others to learn from this (both current and future users thanks to the web based archives of the mailing lists), thus saving us from having to repeat ourselves even more. Thanks for respecting this. If you have found or suspect a security problem in curl or libcurl, [submit all the details to us](https://curl.se/dev/vuln-disclosure.html). We keep the issue private while we investigate, confirm it, work and validate a fix and agree on a time schedule for publication etc. That way we produce a fix in a timely manner before the flaw is announced to the world, reducing the impact the problem risks having on existing users. Security issues can also be taken to the curl security team by emailing security at curl.se (closed list of receivers, mails are not disclosed). ## Where do I buy commercial support for curl? curl is fully open source. It means you can hire any skilled engineer to fix your curl-related problems. We list [available alternatives](https://curl.se/support.html). ## How many are using curl? It is impossible to tell. We do not know how many users that knowingly have installed and use curl. We do not know how many users that use curl without knowing that they are in fact using it. We do not know how many users that downloaded or installed curl and then never use it. In 2025, we estimate that curl runs in roughly thirty billion installations world wide. ## Why do you not update ca-bundle.crt In the curl project we have decided not to attempt to keep this file updated (or even present) since deciding what to add to a CA cert bundle is an undertaking we have not been ready to accept, and the one we can get from Mozilla is perfectly fine so there is no need to duplicate that work. Today, with many services performed over HTTPS, every operating system should come with a default CA cert bundle that can be deemed somewhat trustworthy and that collection (if reasonably updated) should be deemed to be a lot better than a private curl version. If you want the most recent collection of CA certs that Mozilla Firefox uses, we recommend using our online [CA certificate service](https://curl.se/docs/caextract.html) setup for this purpose. ## I have a problem, who can I chat with? There is a bunch of friendly people hanging out in the #curl channel on the IRC network libera.chat. If you are polite and nice, chances are good that you can get -- or provide -- help instantly. ## curl's ECCN number? The US government restricts exports of software that contains or uses cryptography. When doing so, the Export Control Classification Number (ECCN) is used to identify the level of export control etc. Apache Software Foundation has [a good explanation of ECCN](https://www.apache.org/dev/crypto.html). We believe curl's number might be ECCN 5D002, another possibility is 5D992. It seems necessary to write them (the authority that administers ECCN numbers), asking to confirm. Comprehensible explanations of the meaning of such numbers and how to obtain them (resp.) are [here](https://www.bis.gov/licensing/classify-your-item) and [here](https://www.bis.gov/licensing/classify-your-item/publicly-available-classification-information). An incomprehensible description of the two numbers above is available on [bis.doc.gov](https://www.bis.doc.gov/index.php/documents/new-encryption/1653-ccl5-pt2-3) ## How do I submit my patch? We strongly encourage you to submit changes and improvements directly as [pull requests on GitHub](https://github.com/curl/curl/pulls). If you cannot or choose not to engage with GitHub, send your patch to the curl-library mailing list. We are many subscribers there and there are lots of people who can review patches, comment on them and receive them properly. Many more details are found in the [contribute](https://curl.se/dev/contribute.html) and [internals](https://curl.se/dev/internals.html) documents. ## How do I port libcurl to my OS? Here's a rough step-by-step: 1. copy a suitable `lib/config-*.h` file as a start to `lib/config-[youros].h` 2. edit `lib/config-[youros].h` to match your OS and setup 3. edit `lib/curl_setup.h` to include `config-[youros].h` when your OS is detected by the preprocessor, in the style others already exist 4. compile `lib/*.c` and make them into a library # Install ## configure fails when using static libraries You may find that configure fails to properly detect the entire dependency chain of libraries when you provide static versions of the libraries that configure checks for. The reason why static libraries are much harder to deal with is that for them we do not get any help but the script itself must know or check what more libraries that are needed (with shared libraries, that dependency chain is handled automatically). This is an error-prone process and one that also tends to vary over time depending on the release versions of the involved components and may also differ between operating systems. For that reason, configure does few attempts to actually figure this out and you are instead encouraged to set `LIBS` and `LDFLAGS` accordingly when you invoke configure, and point out the needed libraries and set the necessary flags yourself. ## Does curl work with other SSL libraries? curl has been written to use a generic SSL function layer internally, and that SSL functionality can then be provided by one out of many different SSL backends. curl can be built to use one of the following SSL alternatives: AWS-LC, BoringSSL, GnuTLS, LibreSSL, OpenSSL, mbedTLS, Rustls, Schannel (native Windows), or wolfSSL. They all have their pros and cons, and we maintain [a TLS library comparison](https://curl.se/docs/ssl-compared.html). ## How do I upgrade curl.exe in Windows? The curl tool that is shipped as an integrated component of Windows 10 and Windows 11 is managed by Microsoft. If you were to delete the file or replace it with a newer version downloaded from [the curl website](https://curl.se/windows/), then Windows Update ceases to work on your system. There is no way to independently force an upgrade of the curl.exe that is part of Windows other than through the regular Windows update process. There is also nothing the curl project itself can do about this, since this is managed and controlled entirely by Microsoft as owners of the operating system. You can always download and install [the latest version of curl for Windows](https://curl.se/windows/) into a separate location. ## Does curl support SOCKS (RFC 1928) ? Yes, SOCKS 4 and 5 are supported. # Usage ## curl: (1) SSL is disabled, https: not supported If you get this output when trying to get anything from an HTTPS server, it means that the instance of curl/libcurl that you are using was built without support for this protocol. This could have happened if the configure script that was run at build time could not find all libs and include files curl requires for SSL to work. If the configure script fails to find them, curl is built without SSL support. To get HTTPS support into a curl that was previously built but that reports that HTTPS is not supported, you should dig through the document and logs and check out why the configure script does not find the SSL libs and/or include files. ## How do I tell curl to resume a transfer? curl supports resumed transfers both ways on both FTP and HTTP. Try the `-C` option. ## Why does my posting using -F not work? You cannot arbitrarily use `-F` or `-d`, the choice between `-F` or `-d` depends on the HTTP operation you need curl to do and what the web server that receives your post expects. If the form you are trying to submit uses the type 'multipart/form-data', then and only then you must use the -F type. In all the most common cases, you should use `-d` which then causes a posting with the type `application/x-www-form-urlencoded`. This is described in some detail in the [Manual](https://curl.se/docs/tutorial.html) and [The Art Of HTTP Scripting](https://curl.se/docs/httpscripting.html) documents, and if you do not understand it the first time, read it again before you post questions about this to the mailing list. Also, try reading through the mailing list archives for old postings and questions regarding this. ## How do I tell curl to run custom FTP commands? You can tell curl to perform optional commands both before and/or after a file transfer. Study the `-Q`/`--quote` option. Since curl is used for file transfers, you do not normally use curl to perform FTP commands without transferring anything. Therefore you must always specify a URL to transfer to/from even when doing custom FTP commands, or use `-I` which implies the *no body* option sent to libcurl. ## How can I disable the Accept: header? You can change this and all internally generated headers by adding a replacement with the `-H`/`--header` option. By adding a header with empty contents you safely disable that one. Use `-H Accept:` to disable that specific header. ## Does curl support ASP, XML, XHTML or HTML version Y? To curl, all contents are alike. It does not matter how the page was generated. It may be ASP, PHP, Perl, shell-script, SSI or plain HTML files. There is no difference to curl and it does not even know what kind of language that generated the page. See also the separate question about JavaScript. ## Can I use curl to delete/rename a file through FTP? Yes. You specify custom FTP commands with `-Q`/`--quote`. One example would be to delete a file after you have downloaded it: curl -O ftp://example.com/coolfile -Q '-DELE coolfile' or rename a file after upload: curl -T infile ftp://example.com/dir/ -Q "-RNFR infile" -Q "-RNTO newname" ## How do I tell curl to follow HTTP redirects? curl does not follow so-called redirects by default. The `Location:` header that informs the client about this is only interpreted if you are using the `-L`/`--location` option. As in: curl -L https://example.com Not all redirects are HTTP ones. See [Redirects work in browser but not with curl](#redirects-work-in-browser-but-not-with-curl) ## How do I use curl in my favorite programming language? Many programming languages have interfaces and bindings that allow you to use curl without having to use the command line tool. If you are fluent in such a language, you may prefer to use one of these interfaces instead. Find out more about which languages that support curl directly, and how to install and use them, in the [libcurl section of the curl website](https://curl.se/libcurl/). All the various bindings to libcurl are made by other projects and people, outside of the curl project. The curl project itself only produces libcurl with its plain C API. If you do not find anywhere else to ask you can ask about bindings on the curl-library list too, but be prepared that people on that list may not know anything about bindings. In December 2025 there were around **60** different [interfaces available](https://curl.se/libcurl/bindings.html) for almost any language you can imagine. ## What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP? curl adheres to the HTTP spec, which means you can play with *any* protocol that is built on top of HTTP. Protocols such as SOAP, WebDAV and XML-RPC are all such ones. You can use `-X` to set custom requests and -H to set custom headers (or replace internally generated ones). Using libcurl of course also works and you would use the proper library options to do the same. ## How do I POST with a different Content-Type? You can always replace the internally generated headers with `-H`/`--header`. To make a simple HTTP POST with `text/xml` as content-type, do something like: curl -d "datatopost" -H "Content-Type: text/xml" [URL] ## Why do FTP-specific features over HTTP proxy fail? Because when you use an HTTP proxy, the protocol spoken on the network is HTTP, even if you specify an FTP URL. This effectively means that you normally cannot use FTP-specific features such as FTP upload and FTP quote etc. There is one exception to this rule, and that is if you can *tunnel through* the given HTTP proxy. Proxy tunneling is enabled with a special option (`-p`) and is generally not available as proxy admins usually disable tunneling to ports other than 443 (which is used for HTTPS access through proxies). ## Why do my single/double quotes fail? To specify a command line option that includes spaces, you might need to put the entire option within quotes. Like in: curl -d " with spaces " example.com or perhaps curl -d ' with spaces ' example.com Exactly what kind of quotes and how to do this is entirely up to the shell or command line interpreter that you are using. For most Unix shells, you can more or less pick either single (`'`) or double (`"`) quotes. For Windows/DOS command prompts you must use double (") quotes, and if the option string contains inner double quotes you can escape them with a backslash. For Windows PowerShell the arguments are not always passed on as expected because curl is not a PowerShell script. You may or may not be able to use single quotes. To escape inner double quotes seems to require a backslash-backtick escape sequence and the outer quotes as double quotes. Please study the documentation for your particular environment. Examples in the curl docs use a mix of both of these as shown above. You must adjust them to work in your environment. Remember that curl works and runs on more operating systems than most single individuals have ever tried. ## Does curl support JavaScript or PAC (automated proxy config)? Many webpages do stuff using embedded JavaScript. curl and libcurl have no built-in support for that, so it is treated like any other contents. `.pac` files are a Netscape invention and are sometimes used by organizations to allow them to differentiate which proxies to use. The `.pac` contents is a JavaScript program that gets invoked by the browser and that returns the name of the proxy to connect to. Since curl does not support JavaScript, it cannot support .pac proxy configuration either. Some workarounds usually suggested to overcome this JavaScript dependency: Depending on the JavaScript complexity, write up a script that translates it to another language and execute that. Read the JavaScript code and rewrite the same logic in another language. Implement a JavaScript interpreter, people have successfully used the Mozilla JavaScript engine in the past. Ask your admins to stop this, for a static proxy setup or similar. ## Can I do recursive fetches with curl? No. curl itself has no code that performs recursive operations, such as those performed by Wget and similar tools. There exists curl using scripts with that functionality, and you can write programs based on libcurl to do it, but the command line tool curl itself cannot. ## What certificates do I need when I use SSL? There are three different kinds of certificates to keep track of when we talk about using SSL-based protocols (HTTPS or FTPS) using curl or libcurl. ### Client certificate The server you communicate with may require that you can provide this in order to prove that you actually are who you claim to be. If the server does not require this, you do not need a client certificate. A client certificate is always used together with a private key, and the private key has a passphrase that protects it. ### Server certificate The server you communicate with has a server certificate. You can and should verify this certificate to make sure that you are truly talking to the real server and not a server impersonating it. Servers often also provide an intermediate certificate. It acts as a bridge between a website's SSL certificate and a Certificate Authority's (CA) root certificate, creating a "chain of trust". ### Certificate Authority Certificate ("CA cert") You often have several CA certs in a CA cert bundle that can be used to verify a server certificate that was signed by one of the authorities in the bundle. curl does not come with a CA cert bundle but most curl installs provide one. You can also override the default. Server certificate verification is enabled by default in curl and libcurl. Server certificates that are *self-signed* or otherwise signed by a CA that you do not have a CA cert for, cannot be verified. If the verification during a connect fails, you are refused access. You then might have to explicitly disable the verification to connect to the server. ## How do I list the root directory of an FTP server? There are two ways. The way defined in the RFC is to use an encoded slash in the first path part. List the `/tmp` directory like this: curl ftp://ftp.example.com/%2ftmp/ The second way is non-standard but more readable; start the path section of the URL with a slash: curl ftp://ftp.example.com//tmp/ ## Can I use curl to send a POST/PUT and not wait for a response? No. You can easily write your own program using libcurl to do such stunts. ## How do I get HTTP from a host using a specific IP address? For example, you may be trying out a website installation that is not yet in the DNS. Or you have a site using multiple IP addresses for a given host name and you want to address a specific one out of the set. Set a custom `Host:` header that identifies the server name you want to reach but use the target IP address in the URL: curl --header "Host: www.example.com" https://somewhere.example/ You can also opt to add faked hostname entries to curl with the --resolve option. That has the added benefit to make things like redirects also work properly. The above operation would instead be done as: curl --resolve www.example.com:80:127.0.0.1 https://www.example.com/ ## How to SFTP from my user's home directory? Contrary to how FTP works, SFTP and SCP URLs specify the exact directory to work with. It means that if you do not specify that you want the user's home directory, you get the actual root directory. To specify a file in your user's home directory, you need to use the correct URL syntax which for SFTP might look similar to: curl -O -u user:password sftp://example.com/~/file.txt and for SCP it is a different protocol prefix: curl -O -u user:password scp://example.com/~/file.txt ## Protocol xxx not supported or disabled in libcurl When passing on a URL to curl to use, it may respond that the particular protocol is not supported or disabled. The particular way this error message is phrased is because curl does not make a distinction internally of whether a particular protocol is not supported (i.e. never got any code added that knows how to speak that protocol) or if it was explicitly disabled. curl can be built to only support a given set of protocols, and the rest would then be disabled or not supported. Note that this error also occurs if you pass a wrongly spelled protocol part as in `htpts://example.com` or as in the less evident case if you prefix the protocol part with a space as in `" https://example.com/"`. ## curl `-X` gives me HTTP problems In normal circumstances, `-X` should hardly ever be used. By default you use curl without explicitly saying which request method to use when the URL identifies an HTTP transfer. If you pass in a URL like `curl https://example.com` it uses GET. If you use `-d` or `-F`, curl uses POST, `-I` causes a HEAD and `-T` makes it a PUT. If for whatever reason you are not happy with these default choices that curl does for you, you can override those request methods by specifying `-X [WHATEVER]`. This way you can for example send a DELETE by doing `curl -X DELETE [URL]`. It is thus pointless to do `curl -XGET [URL]` as GET would be used anyway. In the same vein it is pointless to do `curl -X POST -d data [URL]`. You can make a fun and somewhat rare request that sends a request-body in a GET request with something like `curl -X GET -d data [URL]`. Note that `-X` does not actually change curl's behavior as it only modifies the actual string sent in the request, but that may of course trigger a different set of events. Accordingly, by using `-XPOST` on a command line that for example would follow a 303 redirect, you effectively prevent curl from behaving correctly. Be aware. # Running ## Why do I get problems when I use & or % in the URL? In general Unix shells, the & symbol is treated specially and when used, it runs the specified command in the background. To safely send the & as a part of a URL, you should quote the entire URL by using single (`'`) or double (`"`) quotes around it. Similar problems can also occur on some shells with other characters, including ?*!$~(){}<>\|;`. When in doubt, quote the URL. An example that would invoke a remote CGI that uses &-symbols could be: curl 'https://www.example.com/cgi-bin/query?text=yes&q=curl' In Windows, the standard DOS shell treats the percent sign specially and you need to use TWO percent signs for each single one you want to use in the URL. If you want a literal percent sign to be part of the data you pass in a POST using `-d`/`--data` you must encode it as `%25` (which then also needs the percent sign doubled on Windows machines). ## How can I use {, }, [ or ] to specify multiple URLs? Because those letters have a special meaning to the shell, to be used in a URL specified to curl you must quote them. An example that downloads two URLs (sequentially) would be: curl '{curl,www}.haxx.se' To be able to use those characters as actual parts of the URL (without using them for the curl URL *globbing* system), use the `-g`/`--globoff` option: curl -g 'www.example.com/weirdname[].html' ## Why do I get downloaded data even though the webpage does not exist? curl asks remote servers for the page you specify. If the page does not exist at the server, the HTTP protocol defines how the server should respond and that means that headers and a page get returned. That is how HTTP works. By using the `--fail` option you can tell curl explicitly to not get any data if the HTTP return code does not say success. ## Why do I get return code XXX from an HTTP server? RFC 2616 clearly explains the return codes. This is a short transcript. Go read the RFC for exact details: ### 400 Bad Request The request could not be understood by the server due to malformed syntax. The client SHOULD NOT repeat the request without modifications. ### 401 Unauthorized The request requires user authentication. ### 403 Forbidden The server understood the request, but is refusing to fulfill it. Authorization cannot help and the request SHOULD NOT be repeated. ### 404 Not Found The server has not found anything matching the Request-URI. No indication is given as to whether the condition is temporary or permanent. ### 405 Method Not Allowed The method specified in the Request-Line is not allowed for the resource identified by the Request-URI. The response MUST include an `Allow:` header containing a list of valid methods for the requested resource. ### 301 Moved Permanently If you get this return code and an HTML output similar to this: <H1>Moved Permanently</H1> The document has moved <A HREF="https://same_url_now_with_a_trailing_slash.example/">here</A>. it might be because you requested a directory URL but without the trailing slash. Try the same operation again _with_ the trailing URL, or use the `-L`/`--location` option to follow the redirection. ## Can you tell me what error code 142 means? All curl error codes are described at the end of the man page, in the section called **EXIT CODES**. Error codes that are larger than the highest documented error code means that curl has exited due to a crash. This is a serious error, and we appreciate a detailed bug report from you that describes how we could go ahead and repeat this. ## How do I keep usernames and passwords secret in curl command lines? This problem has two sides: The first part is to avoid having clear-text passwords in the command line so that they do not appear in *ps* outputs and similar. That is easily avoided by using the `-K` option to tell curl to read parameters from a file or stdin to which you can pass the secret info. curl itself also attempts to hide the given password by blanking out the option - this does not work on all platforms. To keep the passwords in your account secret from the rest of the world is not a task that curl addresses. You could of course encrypt them somehow to at least hide them from being read by human eyes, but that is not what anyone would call security. Also note that regular HTTP (using Basic authentication) and FTP passwords are sent as cleartext across the network. All it takes for anyone to fetch them is to listen on the network. Eavesdropping is easy. Use more secure authentication methods (like Digest, Negotiate or even NTLM) or consider the SSL-based alternatives HTTPS and FTPS. ## I found a bug It is not a bug if the behavior is documented. Read the docs first. Especially check out the KNOWN_BUGS file, it may be a documented bug. If it is a problem with a binary you have downloaded or a package for your particular platform, try contacting the person who built the package/archive you have. If there is a bug, read the BUGS document first. Then report it as described in there. ## curl cannot authenticate to a server that requires NTLM? NTLM support requires OpenSSL, GnuTLS, mbedTLS or Microsoft Windows libraries at build-time to provide this functionality. ## My HTTP request using HEAD, PUT or DELETE does not work Many web servers allow or demand that the administrator configures the server properly for these requests to work on the web server. Some servers seem to support HEAD only on certain kinds of URLs. To fully grasp this, try the documentation for the particular server software you are trying to interact with. This is not anything curl can do anything about. ## Why do my HTTP range requests return the full document? Because the range may not be supported by the server, or the server may choose to ignore it and return the full document anyway. ## Why do I get "certificate verify failed" ? When you invoke curl and get an error 60 error back it means that curl could not verify that the server's certificate was good. curl verifies the certificate using the CA cert bundle and verifying for which names the certificate has been granted. To completely disable the certificate verification, use `-k`. This does however enable man-in-the-middle attacks and makes the transfer **insecure**. We strongly advise against doing this for more than experiments. If you get this failure with a CA cert bundle installed and used, the server's certificate might not be signed by one of the certificate authorities in your CA store. It might for example be self-signed. You then correct this problem by obtaining a valid CA cert for the server. Or again, decrease the security by disabling this check. At times, you find that the verification works in your favorite browser but fails in curl. When this happens, the reason is usually that the server sends an incomplete cert chain. The server is mandated to send all *intermediate certificates* but does not. This typically works with browsers anyway since they A) cache such certs and B) supports AIA which downloads such missing certificates on demand. This is a bad server configuration. A good way to figure out if this is the case it to use [the SSL Labs server](https://www.ssllabs.com/ssltest/) test and check the certificate chain. Details are also in [the SSL certificates document](https://curl.se/docs/sslcerts.html). ## Why is curl -R on Windows one hour off? Since curl 7.53.0 this issue should be fixed as long as curl was built with any modern compiler that allows for a 64-bit curl_off_t type. For older compilers or prior curl versions it may set a time that appears one hour off. This happens due to a flaw in how Windows stores and uses file modification times and it is not easily worked around. For more details [read this](https://web.archive.org/web/20050715084352/codeproject.com/datetime/dstbugs.asp). ## Redirects work in browser but not with curl curl supports HTTP redirects well (see a previous question above). Browsers generally support at least two other ways to perform redirects that curl does not: Meta tags. You can write an HTML tag that causes the browser to redirect to another given URL after a certain time. JavaScript. You can write a JavaScript program embedded in an HTML page that redirects the browser to another given URL. There is no way to make curl follow these redirects. You must either manually figure out what the page is set to do, or write a script that parses the results and fetches the new URL. ## FTPS does not work curl supports FTPS (sometimes known as FTP-SSL) both implicit and explicit mode. When a URL is used that starts with `ftps://`, curl assumes implicit SSL on the control connection and therefore immediately connects and tries to speak SSL. `ftps://` connections default to port 990. To use explicit FTPS, you use an `ftp://` URL and the `--ssl-reqd` option (or one of its related flavors). This is the most common method, and the one mandated by RFC 4217. This kind of connection then of course uses the standard FTP port 21 by default. ## My HTTP POST or PUT requests are slow libcurl makes all POST and PUT requests (except for requests with a small request body) use the `Expect: 100-continue` header. This header allows the server to deny the operation early so that libcurl can bail out before having to send any data. This is useful in authentication cases and others. Many servers do not implement the `Expect:` stuff properly and if the server does not respond (positively) within 1 second libcurl continues and sends off the data anyway. You can disable libcurl's use of the `Expect:` header the same way you disable any header, using `-H` / `CURLOPT_HTTPHEADER`, or by forcing it to use HTTP 1.0. ## Non-functional connect timeouts In most Windows setups having a timeout longer than 21 seconds makes no difference, as it only sends 3 TCP SYN packets and no more. The second packet sent three seconds after the first and the third six seconds after the second. No more than three packets are sent, no matter how long the timeout is set. See Windows option `TcpMaxConnectRetransmissions` for more. Also, even on non-Windows systems there may run a firewall or anti-virus software or similar that accepts the connection but does not actually do anything else. This makes (lib)curl to consider the connection connected and thus the connect timeout does not trigger. ## `file://` URLs containing drive letters (Windows, NetWare) When using curl to try to download a local file, one might use a URL in this format: file://D:/blah.txt you find that even if `D:\blah.txt` does exist, curl returns a 'file not found' error. According to [RFC 1738](https://datatracker.ietf.org/doc/html/rfc1738), `file://` URLs must contain a host component, but it is ignored by most implementations. In the above example, `D:` is treated as the host component, and is taken away. Thus, curl tries to open `/blah.txt`. If your system is installed to drive C:, that resolves to `C:\blah.txt`, and if that does not exist you get the not found error. To fix this problem, use `file://` URLs with *three* leading slashes: file:///D:/blah.txt Alternatively, if it makes more sense, specify `localhost` as the host component: file://localhost/D:/blah.txt In either case, curl should now be looking for the correct file. ## Why does not curl return an error when the network cable is unplugged? Unplugging a cable is not an error situation. The TCP/IP protocol stack was designed to be fault tolerant, so even though there may be a physical break somewhere the connection should not be affected, but possibly delayed. Eventually, the physical break gets fixed or the data re-routed around the physical problem through another path. In such cases, the TCP/IP stack is responsible for detecting when the network connection is irrevocably lost. Since with some protocols it is perfectly legal for the client to wait indefinitely for data, the stack may never report a problem, and even when it does, it can take up to 20 minutes for it to detect an issue. The curl option `--keepalive-time` enables keep-alive support in the TCP/IP stack which makes it periodically probe the connection to make sure it is still available to send data. That should reliably detect any TCP/IP network failure. TCP keep alive does not detect the network going down before the TCP/IP connection is established (e.g. during a DNS lookup) or using protocols that do not use TCP. To handle those situations, curl offers a number of timeouts on its own. `--speed-limit`/`--speed-time` aborts if the data transfer rate falls too low, and `--connect-timeout` and `--max-time` can be used to put an overall timeout on the connection phase or the entire transfer. A libcurl-using application running in a known physical environment (e.g. an embedded device with only a single network connection) may want to act immediately if its lone network connection goes down. That can be achieved by having the application monitor the network connection on its own using an OS-specific mechanism, then signaling libcurl to abort. ## curl does not return error for HTTP non-200 responses Correct. Unless you use `-f` (`--fail`) or `--fail-with-body`. When doing HTTP transfers, curl performs exactly what you are asking it to do and if successful it does not return an error. You can use curl to test your web server's "file not found" page (that gets 404 back), you can use it to check your authentication protected webpages (that gets a 401 back) and so on. The specific HTTP response code does not constitute a problem or error for curl. It sends and delivers HTTP as you asked and if that worked, everything is fine and dandy. The response code is generally providing more higher level error information that curl does not care about. The error was not in the HTTP transfer. If you want your command line to treat error codes in the 400 and up range as errors and thus return a non-zero value and possibly show an error message, curl has a dedicated option for that: `-f` (`CURLOPT_FAILONERROR` in libcurl speak). You can also use the `-w` option and the variable `%{response_code}` to extract the exact response code that was returned in the response. # libcurl ## Is libcurl thread-safe? Yes. We have written the libcurl code specifically adjusted for multi-threaded programs. libcurl uses thread-safe functions instead of non-safe ones if your system has such. Note that you must never share the same handle in multiple threads. There may be some exceptions to thread-safety depending on how libcurl was built. Please review [the guidelines for thread safety](https://curl.se/libcurl/c/threadsafe.html) to learn more. ## How can I receive all data into a large memory chunk? (See the [get in memory](https://curl.se/libcurl/c/getinmemory.html) example.) You are in full control of the callback function that gets called every time there is data received from the remote server. You can make that callback do whatever you want. You do not have to write the received data to a file. One solution to this problem could be to have a pointer to a struct that you pass to the callback function. You set the pointer using the CURLOPT_WRITEDATA option. Then that pointer is passed to the callback instead of a FILE * to a file: ~~~c /* store data this struct */ struct MemoryStruct { char *memory; size_t size; }; /* imaginary callback function */ size_t WriteMemoryCallback(void *ptr, size_t size, size_t nmemb, void *data) { size_t realsize = size * nmemb; struct MemoryStruct *mem = (struct MemoryStruct *)data; mem->memory = realloc(mem->memory, mem->size + realsize + 1); if(mem->memory) { memcpy(&(mem->memory[mem->size]), ptr, realsize); mem->size += realsize; mem->memory[mem->size] = 0; } return realsize; } ~~~ ## How do I fetch multiple files with libcurl? libcurl has excellent support for transferring multiple files. You should repeatedly set new URLs with `curl_easy_setopt()` and then transfer it with `curl_easy_perform()`. The handle you get from curl_easy_init() is not only reusable, but you are even encouraged to reuse it if you can, as that enables libcurl to use persistent connections. ## Does libcurl do Winsock initialization on Win32 systems? Yes, if told to in the `curl_global_init()` call. ## Does CURLOPT_WRITEDATA and CURLOPT_READDATA work on Win32 ? Yes, but you cannot open a FILE * and pass the pointer to a DLL and have that DLL use the FILE * (as the DLL and the client application cannot access each others' variable memory areas). If you set `CURLOPT_WRITEDATA` you must also use `CURLOPT_WRITEFUNCTION` as well to set a function that writes the file, even if all it does is write the data to the specified FILE *. Similarly, if you use `CURLOPT_READDATA` you must also specify `CURLOPT_READFUNCTION`. ## What about Keep-Alive or persistent connections? curl and libcurl have excellent support for persistent connections when transferring several files from the same server. curl attempts to reuse connections for all URLs specified on the same command line/config file, and libcurl reuses connections for all transfers that are made using the same libcurl handle. When you use the easy interface the connection cache is kept within the easy handle. If you instead use the multi interface, the connection cache is kept within the multi handle and shared among all the easy handles that are used within the same multi handle. ## Link errors when building libcurl on Windows You need to make sure that your project, and all the libraries (both static and dynamic) that it links against, are compiled/linked against the same run time library. This is determined by the `/MD`, `/ML`, `/MT` (and their corresponding `/M?d`) options to the command line compiler. `/MD` (linking against `MSVCRT.dll`) seems to be the most commonly used option. When building an application that uses the static libcurl library, you must add `-DCURL_STATICLIB` to your `CFLAGS`. Otherwise the linker looks for dynamic import symbols. If you are using Visual Studio, you need to instead add `CURL_STATICLIB` in the "Preprocessor Definitions" section. If you get a linker error like `unknown symbol __imp__curl_easy_init ...` you have linked against the wrong (static) library. If you want to use the libcurl.dll and import lib, you do not need any extra `CFLAGS`, but use one of the import libraries below. These are the libraries produced by the various lib/Makefile.* files: | Target | static lib | import lib for DLL | |----------------|----------------|--------------------| | MinGW | `libcurl.a` | `libcurldll.a` | | MSVC (release) | `libcurl.lib` | `libcurl_imp.lib` | | MSVC (debug) | `libcurld.lib` | `libcurld_imp.lib` | ## libcurl.so.X: open failed: No such file or directory This is an error message you might get when you try to run a program linked with a shared version of libcurl and your runtime linker (`ld.so`) could not find the shared library named `libcurl.so.X`. (Where X is the number of the current libcurl ABI, typically 3 or 4). You need to make sure that `ld.so` finds `libcurl.so.X`. You can do that multiple ways, and it differs somewhat between different operating systems. They are usually: * Add an option to the linker command line that specify the hard-coded path the runtime linker should check for the lib (usually `-R`) * Set an environment variable (`LD_LIBRARY_PATH` for example) where `ld.so` should check for libs * Adjust the system's config to check for libs in the directory where you have put the library (like Linux's `/etc/ld.so.conf`) `man ld.so` and `man ld` tells you more details ## How does libcurl resolve hostnames? libcurl supports a large number of name resolve functions. One of them is picked at build-time and used unconditionally. Thus, if you want to change name resolver function you must rebuild libcurl and tell it to use a different function. ### The non-IPv6 resolver The non-IPv6 resolver that can use one of four different hostname resolve calls depending on what your system supports: 1. gethostbyname() 2. gethostbyname_r() with 3 arguments 3. gethostbyname_r() with 5 arguments 4. gethostbyname_r() with 6 arguments ### The IPv6 resolver Uses getaddrinfo() ### The cares resolver The c-ares based name resolver that uses the c-ares library for resolves. Using this offers asynchronous name resolves. ## The threaded resolver It uses the IPv6 or the non-IPv6 resolver solution in a temporary thread. ## How do I prevent libcurl from writing the response to stdout? libcurl provides a default built-in write function that writes received data to stdout. Set the `CURLOPT_WRITEFUNCTION` to receive the data, or possibly set `CURLOPT_WRITEDATA` to a different FILE * handle. ## How do I make libcurl not receive the whole HTTP response? You make the write callback (or progress callback) return an error and libcurl then aborts the transfer. ## Can I make libcurl fake or hide my real IP address? No. libcurl operates on a higher level. Besides, faking IP address would imply sending IP packets with a made-up source address, and then you normally get a problem with receiving the packet sent back as they would then not be routed to you. If you use a proxy to access remote sites, the sites do not see your local IP address but instead the address of the proxy. Also note that on many networks NATs or other IP-munging techniques are used that makes you see and use a different IP address locally than what the remote server is seeing you coming from. You may also consider using [Tor](https://www.torproject.org/). ## How do I stop an ongoing transfer? With the easy interface you make sure to return the correct error code from one of the callbacks, but none of them are instant. There is no function you can call from another thread or similar that stops it immediately. Instead, you need to make sure that one of the callbacks you use returns an appropriate value that stops the transfer. Suitable callbacks that you can do this with include the progress callback, the read callback and the write callback. If you are using the multi interface, you can also stop a transfer by removing the particular easy handle from the multi stack at any moment you think the transfer is done or when you wish to abort the transfer. ## Using C++ non-static functions for callbacks? libcurl is a C library, it does not know anything about C++ member functions. You can overcome this limitation with relative ease using a static member function that is passed a pointer to the class: ~~~c++ // f is the pointer to your object. static size_t YourClass::func(char *buffer, size_t sz, size_t n, void *f) { // Call non-static member function. static_cast<YourClass*>(f)->nonStaticFunction(); } // This is how you pass pointer to the static function: curl_easy_setopt(hcurl, CURLOPT_WRITEFUNCTION, YourClass::func); curl_easy_setopt(hcurl, CURLOPT_WRITEDATA, this); ~~~ ## How do I get an FTP directory listing? If you end the FTP URL you request with a slash, libcurl provides you with a directory listing of that given directory. You can also set `CURLOPT_CUSTOMREQUEST` to alter what exact listing command libcurl would use to list the files. The follow-up question tends to be how is a program supposed to parse the directory listing. How does it know what's a file and what's a directory and what's a symlink etc. If the FTP server supports the `MLSD` command then it returns data in a machine-readable format that can be parsed for type. The types are specified by RFC 3659 section 7.5.1. If `MLSD` is not supported then you have to work with what you are given. The `LIST` output format is entirely at the server's own liking and the `NLST` output does not reveal any types and in many cases does not even include all the directory entries. Also, both `LIST` and `NLST` tend to hide Unix-style hidden files (those that start with a dot) by default so you need to do `LIST -a` or similar to see them. Example - List only directories. `ftp.funet.fi` supports `MLSD` and `ftp.kernel.org` does not: curl -s ftp.funet.fi/pub/ -X MLSD | \ perl -lne 'print if s/(?:^|;)type=dir;[^ ]+ (.+)$/$1/' curl -s ftp.kernel.org/pub/linux/kernel/ | \ perl -lne 'print if s/^d[-rwx]{9}(?: +[^ ]+){7} (.+)$/$1/' If you need to parse LIST output, libcurl provides the ability to specify a wildcard to download multiple files from an FTP directory. ## I want a different time-out Sometimes users realize that `CURLOPT_TIMEOUT` and `CURLOPT_CONNECTIMEOUT` are not sufficiently advanced or flexible to cover all the various use cases and scenarios applications end up with. libcurl offers many more ways to time-out operations. A common alternative is to use the `CURLOPT_LOW_SPEED_LIMIT` and `CURLOPT_LOW_SPEED_TIME` options to specify the lowest possible speed to accept before to consider the transfer timed out. The most flexible way is by writing your own time-out logic and using `CURLOPT_XFERINFOFUNCTION` (perhaps in combination with other callbacks) and use that to figure out exactly when the right condition is met when the transfer should get stopped. ## Can I write a server with libcurl? No. libcurl offers no functions or building blocks to build any kind of Internet protocol server. libcurl is only a client-side library. For server libraries, you need to continue your search elsewhere but there exist many good open source ones out there for most protocols you could want a server for. There are also really good stand-alone servers that have been tested and proven for many years. There is no need for you to reinvent them. ## Does libcurl use threads? No, libcurl executes in the same thread you call it in. All callbacks are called in the same thread as the one you call libcurl in. If you want to avoid your thread to be blocked by the libcurl call, you make sure you use the non-blocking multi API which does transfers asynchronously - still in the same single thread. libcurl does potentially internally use threads for name resolving, if it was built to work like that, but in those cases it creates the child threads by itself and they are only used and then killed internally by libcurl and never exposed to the outside. # License curl and libcurl are released under an MIT/X derivative license. The license is liberal and should not impose a problem for your project. This section is a brief summary for the cases we get the most questions. We are not lawyers and this is not legal advice. You should probably consult one if you want true and accurate legal insights without our prejudice. Note especially that this section concerns the libcurl license only; compiling in features of libcurl that depend on other libraries (e.g. OpenSSL) may affect the licensing obligations of your application. ## I have a GPL program, can I use the libcurl library? Yes Since libcurl may be distributed under the MIT/X derivative license, it can be used together with GPL in any software. ## I have a closed-source program, can I use the libcurl library? Yes libcurl does not put any restrictions on the program that uses the library. ## I have a BSD licensed program, can I use the libcurl library? Yes libcurl does not put any restrictions on the program that uses the library. ## I have a program that uses LGPL libraries, can I use libcurl? Yes The LGPL license does not clash with other licenses. ## Can I modify curl/libcurl for my program and keep the changes secret? Yes The MIT/X derivative license practically allows you to do almost anything with the sources, on the condition that the copyright texts in the sources are left intact. ## Can you please change the curl/libcurl license? No. We have carefully picked this license after years of development and discussions and a large amount of people have contributed with source code knowing that this is the license we use. This license puts the restrictions we want on curl/libcurl and it does not spread to other programs or libraries that use it. It should be possible for everyone to use libcurl or curl in their projects, no matter what license they already have in use. ## What are my obligations when using libcurl in my commercial apps? Next to none. All you need to adhere to is the MIT-style license (stated in the COPYING file) which says you have to include the copyright notice in *all copies* and that you may not use the copyright holder's name when promoting your software. You do not have to release any of your source code. You do not have to reveal or make public any changes to the libcurl source code. You do not have to broadcast to the world that you are using libcurl within your app. All we ask is that you disclose *the copyright notice and this permission notice* somewhere. Most probably like in the documentation or in the section where other third party dependencies already are mentioned and acknowledged. As can be seen [here](https://curl.se/docs/companies.html) and elsewhere, more and more companies are discovering the power of libcurl and take advantage of it even in commercial environments. ## What license does curl use exactly? curl is released under an [MIT derivative license](https://curl.se/docs/copyright.html). It is similar but not identical to the MIT license. The difference is considered big enough to make SPDX list it under its own identifier: [curl](https://spdx.org/licenses/curl.html). The changes done to the license that make it uniquely curl were tiny and well-intended, but the reasons for them have been forgotten and we strongly discourage others from doing the same thing. # PHP/CURL ## What is PHP/CURL? The module for PHP that makes it possible for PHP programs to access curl functions from within PHP. In the curl project we call this module PHP/CURL to differentiate it from curl the command line tool and libcurl the library. The PHP team however does not refer to it like this (for unknown reasons). They call it plain CURL (often using all caps) or sometimes ext/curl, but both cause much confusion to users which in turn gives us a higher question load. ## Who wrote PHP/CURL? PHP/CURL was initially written by Sterling Hughes. ## Can I perform multiple requests using the same handle? Yes. After a transfer, you set new options in the handle and make another transfer. This makes libcurl reuse the same connection if it can. ## Does PHP/CURL have dependencies? PHP/CURL is a module that comes with the regular PHP package. It depends on and uses libcurl, so you need to have libcurl installed properly before PHP/CURL can be used. # Development ## Why does curl use C89? As with everything in curl, there is a history and we keep using what we have used before until someone brings up the subject and argues for and works on changing it. We started out using C89 in the 1990s because that was the only way to write a truly portable C program and have it run as widely as possible. C89 was for a long time even necessary to make things work on otherwise considered modern platforms such as Windows. Today, we do not really know how many users that still require the use of a C89 compiler. We continue to use C89 for as long as nobody brings up a strong enough reason for us to change our minds. The core developers of the project do not feel restricted by this and we are not convinced that going C99 offers us enough of a benefit to warrant the risk of cutting off a share of users. ## Would curl be rewritten? In one go: no. Little by little over time? Sure. Over the years, new languages and clever operating environments come and go. Every now and then the urge apparently arises to request that we rewrite curl in another language. Some the most important properties in curl are maintaining the API and ABI for libcurl and keeping the behavior for the command line tool. As long as we can do that, everything else is up for discussion. To maintain the ABI, we probably have to maintain a certain amount of code in C, and to remain rock stable, we never risk anything by rewriting a lot of things in one go. That said, we can certainly offer more and more optional backends written in other languages, as long as those backends can be plugged in at build-time. Backends can be written in any language, but should probably provide APIs usable from C to ease integration and transition. usr/share/doc/alt-curlssl11/TODO.md 0000644 00000114711 15233257616 0012741 0 ustar 00 <!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. SPDX-License-Identifier: curl --> # TODO intro Things to do in project curl. Please tell us what you think, contribute and send us patches that improve things. Be aware that these are things that we could do, or have once been considered things we could do. If you want to work on any of these areas, please consider bringing it up for discussions first on the mailing list so that we all agree it is still a good idea for the project. All bugs documented in the [known_bugs document](https://curl.se/docs/knownbugs.html) are subject for fixing. # libcurl ## Consult `%APPDATA%` also for `.netrc` `%APPDATA%\.netrc` is not considered when running on Windows. Should it not? See [curl issue 4016](https://github.com/curl/curl/issues/4016) ## `struct lifreq` Use `struct lifreq` and `SIOCGLIFADDR` instead of `struct ifreq` and `SIOCGIFADDR` on newer Solaris versions as they claim the latter is obsolete. To support IPv6 interface addresses for network interfaces properly. ## alt-svc sharing The share interface could benefit from allowing the alt-svc cache to be possible to share between easy handles. See [curl issue 4476](https://github.com/curl/curl/issues/4476) The share interface offers CURL_LOCK_DATA_CONNECT to have multiple easy handle share a connection cache, but due to how connections are used they are still not thread-safe when used shared. See [curl issue 4915](https://github.com/curl/curl/issues/4915) and lib1541.c The share interface offers CURL_LOCK_DATA_HSTS to have multiple easy handle share an HSTS cache, but this is not thread-safe. ## thread-safe sharing Using the share interface users can share some data between easy handles but several of the sharing options are documented as not safe and supported to share between multiple concurrent threads. Fixing this would enable more users to share data in more powerful ways. ## updated DNS server while running If `/etc/resolv.conf` gets updated while a program using libcurl is running, it is may cause name resolves to fail unless `res_init()` is called. We should consider calling `res_init()` + retry once unconditionally on all name resolve failures to mitigate against this. Firefox works like that. Note that Windows does not have `res_init()` or an alternative. [curl issue 2251](https://github.com/curl/curl/issues/2251) ## c-ares and CURLOPT_OPENSOCKETFUNCTION curl creates most sockets via the CURLOPT_OPENSOCKETFUNCTION callback and close them with the CURLOPT_CLOSESOCKETFUNCTION callback. c-ares does not use those functions and instead opens and closes the sockets itself. This means that when curl passes the c-ares socket to the CURLMOPT_SOCKETFUNCTION it is not owned by the application like other sockets. See [curl issue 2734](https://github.com/curl/curl/issues/2734) ## Monitor connections in the connection pool libcurl's connection cache or pool holds a number of open connections for the purpose of possible subsequent connection reuse. It may contain a few up to a significant amount of connections. Currently, libcurl leaves all connections as they are and first when a connection is iterated over for matching or reuse purpose it is verified that it is still alive. Those connections may get closed by the server side for idleness or they may get an HTTP/2 ping from the peer to verify that they are still alive. By adding monitoring of the connections while in the pool, libcurl can detect dead connections (and close them) better and earlier, and it can handle HTTP/2 pings to keep such ones alive even when not actively doing transfers on them. ## Try to URL encode given URL Given a URL that for example contains spaces, libcurl could have an option that would try somewhat harder than it does now and convert spaces to %20 and perhaps URL encoded byte values over 128 etc (do what the redirect following code already does). [curl issue 514](https://github.com/curl/curl/issues/514) ## Add support for IRIs IRIs (RFC 3987) allow localized, non-ASCII, names in the URL. To properly support this, curl/libcurl would need to translate/encode the given input from the input string encoding into percent encoded output "over the wire". To make that work smoothly for curl users even on Windows, curl would probably need to be able to convert from several input encodings. ## try next proxy if one does not work Allow an application to specify a list of proxies to try, and failing to connect to the first go on and try the next instead until the list is exhausted. Browsers support this feature at least when they specify proxies using `PAC`. [curl issue 896](https://github.com/curl/curl/issues/896) ## provide timing info for each redirect curl and libcurl provide timing information via a set of different time-stamps (CURLINFO_*_TIME). When curl is following redirects, those returned time value are the accumulated sums. An improvement could be to offer separate timings for each redirect. [curl issue 6743](https://github.com/curl/curl/issues/6743) ## CURLINFO_PAUSE_STATE Return information about the transfer's current pause state, in both directions. See [curl issue 2588](https://github.com/curl/curl/issues/2588) ## Expose tried IP addresses that failed When libcurl fails to connect to a host, it could offer the application the addresses that were used in the attempt. Source + destination IP, source + destination port and protocol (UDP or TCP) for each failure. Possibly as a callback. Perhaps also provide reason. [curl issue 2126](https://github.com/curl/curl/issues/2126) ## erase secrets from heap/stack after use Introducing a concept and system to erase secrets from memory after use, it could help mitigate and lessen the impact of (future) security problems etc. However: most secrets are passed to libcurl as clear text from the application and then clearing them within the library adds nothing... [curl issue 7268](https://github.com/curl/curl/issues/7268) ## make DoH inherit more transfer properties Some options are not inherited because they are not relevant for the DoH SSL connections, or inheriting the option may result in unexpected behavior. For example the user's debug function callback is not inherited because it would be unexpected for internal handles (i.e DoH handles) to be passed to that callback. If an option is not inherited then it is not possible to set it separately for DoH without a DoH-specific option. For example: `CURLOPT_DOH_SSL_VERIFYHOST`, `CURLOPT_DOH_SSL_VERIFYPEER` and `CURLOPT_DOH_SSL_VERIFYSTATUS`. See [curl issue 6605](https://github.com/curl/curl/issues/6605) # libcurl - multi interface ## More non-blocking Make sure we do not ever loop because of non-blocking sockets returning `EWOULDBLOCK` or similar. Blocking cases include: - Name resolves on non-Windows unless c-ares or the threaded resolver is used. - The threaded resolver may block on cleanup: [curl issue 4852](https://github.com/curl/curl/issues/4852) - `file://` transfers - TELNET transfers - GSSAPI authentication for FTP transfers - The "DONE" operation (post transfer protocol-specific actions) for the protocols SFTP, SMTP, FTP. Fixing `multi_done()` for this is a worthy task. - `curl_multi_remove_handle()` for any of the above. - Calling `curl_ws_send()` from a callback ## Better support for same name resolves If a name resolve has been initiated for a given name and a second easy handle wants to resolve that same name as well, make it wait for the first resolve to end up in the cache instead of doing a second separate resolve. This is especially needed when adding many simultaneous handles using the same hostname when the DNS resolver can get flooded. ## Non-blocking `curl_multi_remove_handle()` The multi interface has a few API calls that assume a blocking behavior, like `add_handle()` and `remove_handle()` which limits what we can do internally. The multi API need to be moved even more into a single function that "drives" everything in a non-blocking manner and signals when something is done. A remove or add would then only ask for the action to get started and then `multi_perform()` etc still be called until the add/remove is completed. ## Split connect and authentication process The multi interface treats the authentication process as part of the connect phase. As such any failures during authentication does not trigger the relevant QUIT or LOGOFF for protocols such as IMAP, POP3 and SMTP. ## Edge-triggered sockets should work The multi_socket API should work with edge-triggered socket events. One of the internal actions that need to be improved for this to work perfectly is the `maxloops` handling in `transfer.c:readwrite_data()`. ## multi upkeep In libcurl 7.62.0 we introduced `curl_easy_upkeep`. It unfortunately only works on easy handles. We should introduces a version of that for the multi handle, and also consider doing `upkeep` automatically on connections in the connection pool when the multi handle is in used. See [curl issue 3199](https://github.com/curl/curl/issues/3199) ## Virtual external sockets libcurl performs operations on the given file descriptor that presumes it is a socket and an application cannot replace them at the moment. Allowing an application to fully replace those would allow a larger degree of freedom and flexibility. See [curl issue 5835](https://github.com/curl/curl/issues/5835) ## dynamically decide to use socketpair For users who do not use `curl_multi_wait()` or do not care for `curl_multi_wakeup()`, we could introduce a way to make libcurl NOT create a socketpair in the multi handle. See [curl issue 4829](https://github.com/curl/curl/issues/4829) # Documentation ## Improve documentation about fork safety See [curl issue 6968](https://github.com/curl/curl/issues/6968) # FTP ## A fixed directory listing format Since listing the contents of a remove directory with FTP is returning the list in a format and style the server likes without any established or even defacto standard existing, it would be a feature to users if curl could parse the directory listing and output a general curl format that is fixed and the same, independent of the server's choice. This would allow users to better and more reliably extract information about remote content via FTP directory listings. ## GSSAPI via Windows SSPI In addition to currently supporting the SASL GSSAPI mechanism (Kerberos V5) via third-party GSS-API libraries, such as MIT Kerberos, also add support for GSSAPI authentication via Windows SSPI. ## STAT for LIST without data connection Some FTP servers allow STAT for listing directories instead of using LIST, and the response is then sent over the control connection instead of as the otherwise used data connection. This is not detailed in any FTP specification. ## Passive transfer could try other IP addresses When doing FTP operations through a proxy at localhost, the reported spotted that curl only tried to connect once to the proxy, while it had multiple addresses and a failed connect on one address should make it try the next. After switching to passive mode (EPSV), curl could try all IP addresses for `localhost`. Currently it tries `::1`, but it should also try `127.0.0.1`. See [curl issue 1508](https://github.com/curl/curl/issues/1508) # HTTP ## Provide the error body from a CONNECT response When curl receives a body response from a CONNECT request to a proxy, it always reads and ignores it. It would make some users happy if curl instead optionally would be able to make that responsible available. Via a new callback? Through some other means? See [curl issue 9513](https://github.com/curl/curl/issues/9513) ## Obey `Retry-After` in redirects The `Retry-After` response header is said to dictate "the minimum time that the user agent is asked to wait before issuing the redirected request" and libcurl does not obey this. See [curl issue 11447](https://github.com/curl/curl/issues/11447) ## Rearrange request header order Server implementers often make an effort to detect browser and to reject clients it can detect to not match. One of the last details we cannot yet control in libcurl's HTTP requests, which also can be exploited to detect that libcurl is in fact used even when it tries to impersonate a browser, is the order of the request headers. I propose that we introduce a new option in which you give headers a value, and then when the HTTP request is built it sorts the headers based on that number. We could then have internally created headers use a default value so only headers that need to be moved have to be specified. ## Allow SAN names in HTTP/2 server push curl only allows HTTP/2 push promise if the provided :authority header value exactly matches the hostname given in the URL. It could be extended to allow any name that would match the Subject Alternative Names in the server's TLS certificate. See [curl pull request 3581](https://github.com/curl/curl/pull/3581) ## `auth=` in URLs Add the ability to specify the preferred authentication mechanism to use by using `;auth=<mech>` in the login part of the URL. For example: `http://test:pass;auth=NTLM@example.com` would be equivalent to specifying `--user test:pass;auth=NTLM` or `--user test:pass --ntlm` from the command line. Additionally this should be implemented for proxy base URLs as well. ## Require HTTP version X or higher curl and libcurl provide options for trying higher HTTP versions (for example HTTP/2) but then still allows the server to pick version 1.1. We could consider adding a way to require a minimum version. See [curl issue 7980](https://github.com/curl/curl/issues/7980) # TELNET ## ditch stdin Reading input (to send to the remote server) on stdin is a crappy solution for library purposes. We need to invent a good way for the application to be able to provide the data to send. ## ditch telnet-specific select Move the telnet support's network `select()` loop go away and merge the code into the main transfer loop. Until this is done, the multi interface does not work for telnet. ## feature negotiation debug data Add telnet feature negotiation data to the debug callback as header data. ## exit immediately upon connection if stdin is /dev/null If it did, curl could be used to probe if there is an server there listening on a specific port. That is, the following command would exit immediately after the connection is established with exit code 0: curl -s --connect-timeout 2 telnet://example.com:80 </dev/null # SMTP ## Pass NOTIFY option to CURLOPT_MAIL_RCPT Is there a way to pass the NOTIFY option to the CURLOPT_MAIL_RCPT option ? I set a string that already contains a bracket. For instance something like that: `curl_slist_append(recipients, "<foo@bar> NOTIFY=SUCCESS,FAILURE");`. [curl issue 8232](https://github.com/curl/curl/issues/8232) ## Enhanced capability support Add the ability, for an application that uses libcurl, to obtain the list of capabilities returned from the EHLO command. ## Add `CURLOPT_MAIL_CLIENT` option Rather than use the URL to specify the mail client string to present in the `HELO` and `EHLO` commands, libcurl should support a new `CURLOPT` specifically for specifying this data as the URL is non-standard and to be honest a bit of a hack. Please see the following thread for more information: https://curl.se/mail/lib-2012-05/0178.html # POP3 ## Enhanced capability support Add the ability, for an application that uses libcurl, to obtain the list of capabilities returned from the CAPA command. # IMAP ## Enhanced capability support Add the ability, for an application that uses libcurl, to obtain the list of capabilities returned from the CAPABILITY command. # LDAP ## SASL based authentication mechanisms Currently the LDAP module only supports `ldap_simple_bind_s()` in order to bind to an LDAP server. This function sends username and password details using the simple authentication mechanism (as clear text). It should be possible to use `ldap_bind_s()` instead specifying the security context information ourselves. ## `CURLOPT_SSL_CTX_FUNCTION` for LDAPS `CURLOPT_SSL_CTX_FUNCTION` works perfectly for HTTPS and email protocols, but it has no effect for LDAPS connections. [curl issue 4108](https://github.com/curl/curl/issues/4108) ## Paged searches on LDAP server [curl issue 4452](https://github.com/curl/curl/issues/4452) ## Certificate-Based Authentication LDAPS not possible with macOS and Windows with Certificate-Based Authentication [curl issue 9641](https://github.com/curl/curl/issues/9641) # SMB ## Support modern versions curl only supports version 1, which barely anyone is using anymore. ## File listing support Add support for listing the contents of an SMB share. The output should probably be the same as/similar to FTP. ## Honor file timestamps The timestamp of the transferred file should reflect that of the original file. ## Use NTLMv2 Currently the SMB authentication uses NTLMv1. ## Create remote directories Support for creating remote directories when uploading a file to a directory that does not exist on the server, like `--ftp-create-dirs`. # FILE ## Directory listing on non-POSIX Listing the contents of a directory accessed with FILE only works on platforms with `opendir()`. Support could be added for more systems, like Windows. # TLS ## `TLS-PSK` with OpenSSL Transport Layer Security pre-shared key cipher suites (`TLS-PSK`) is a set of cryptographic protocols that provide secure communication based on pre-shared keys (`PSK`). These pre-shared keys are symmetric keys shared in advance among the communicating parties. [curl issue 5081](https://github.com/curl/curl/issues/5081) ## TLS channel binding TLS 1.2 and 1.3 provide the ability to extract some secret data from the TLS connection and use it in the client request (usually in some sort of authentication) to ensure that the data sent is bound to the specific TLS connection and cannot be successfully intercepted by a proxy. This functionality can be used in a standard authentication mechanism such as GSS-API or SCRAM, or in custom approaches like custom HTTP Authentication headers. For TLS 1.2, the binding type is usually `tls-unique`, and for TLS 1.3 it is `tls-exporter`. - https://datatracker.ietf.org/doc/html/rfc5929 - https://datatracker.ietf.org/doc/html/rfc9266 - [curl issue 9226](https://github.com/curl/curl/issues/9226) ## Defeat TLS fingerprinting By changing the order of TLS extensions provided in the TLS handshake, it is sometimes possible to circumvent TLS fingerprinting by servers. The TLS extension order is of course not the only way to fingerprint a client. ## Consider OCSP stapling by default Treat a negative response a reason for aborting the connection. Since OCSP stapling is presumed to get used much less in the future when Let's Encrypt drops the OCSP support, the benefit of this might however be limited. [curl issue 15483](https://github.com/curl/curl/issues/15483) ## Provide callback for cert verification OpenSSL supports a callback for customized verification of the peer certificate, but this does not seem to be exposed in the libcurl APIs. Could it be? There is so much that could be done if it were. ## Less memory massaging with Schannel The Schannel backend does a lot of custom memory management we would rather avoid: the repeated allocation + free in sends and the custom memory + realloc system for encrypted and decrypted data. That should be avoided and reduced for 1) efficiency and 2) safety. ## Support DANE [DNS-Based Authentication of Named Entities (DANE)](https://datatracker.ietf.org/doc/html/rfc6698) is a way to provide SSL keys and certs over DNS using DNSSEC as an alternative to the CA model. A patch was posted on March 7 2013 (https://curl.se/mail/lib-2013-03/0075.html) but it was a too simple approach. See Daniel's comments: https://curl.se/mail/lib-2013-03/0103.html Björn Stenberg once wrote a separate initial take on DANE that was never completed. ## TLS record padding TLS (1.3) offers optional record padding and OpenSSL provides an API for it. I could make sense for libcurl to offer this ability to applications to make traffic patterns harder to figure out by network traffic observers. See [curl issue 5398](https://github.com/curl/curl/issues/5398) ## Support Authority Information Access certificate extension (AIA) AIA can provide various things like certificate revocation lists but more importantly information about intermediate CA certificates that can allow validation path to be fulfilled when the HTTPS server does not itself provide them. Since AIA is about downloading certs on demand to complete a TLS handshake, it is probably a bit tricky to get done right and a serious privacy leak. See [curl issue 2793](https://github.com/curl/curl/issues/2793) ## Some TLS options are not offered for HTTPS proxies Some TLS related options to the command line tool and libcurl are only provided for the server and not for HTTPS proxies. `--proxy-tls-max`, `--proxy-tlsv1.3`, `--proxy-curves` and a few more. For more Documentation on this see: https://curl.se/libcurl/c/tls-options.html [curl issue 12286](https://github.com/curl/curl/issues/12286) ## Make sure we forbid TLS 1.3 post-handshake authentication RFC 8740 explains how using HTTP/2 must forbid the use of TLS 1.3 post-handshake authentication. We should make sure to live up to that. See [curl issue 5396](https://github.com/curl/curl/issues/5396) ## Support the `clienthello` extension Certain stupid networks and middle boxes have a problem with SSL handshake packets that are within a certain size range because how that sets some bits that previously (in older TLS version) were not set. The `clienthello` extension adds padding to avoid that size range. - https://datatracker.ietf.org/doc/html/rfc7685 - [curl issue 2299](https://github.com/curl/curl/issues/2299) ## Share the CA cache For TLS backends that supports CA caching, it makes sense to allow the share object to be used to store the CA cache as well via the share API. Would allow multiple easy handles to reuse the CA cache and save themselves from a lot of extra processing overhead. ## Add missing features to TLS backends The feature matrix at https://curl.se/libcurl/c/tls-options.html shows which features are supported by which TLS backends, and thus also where there are feature gaps. # Proxy ## Retry SOCKS handshake on address type not supported When curl resolves a hostname, it might get a mix of IPv6 and IPv4 returned. curl might then use an IPv6 address with a SOCKS5 proxy, which - if it does not support IPv6 - returns "Address type not supported" and curl exits with that error. Perhaps it is preferred if curl would in this situation instead first retry the SOCKS handshake again for this case and then use one of the IPv4 addresses for the target host. See [curl issue 17222](https://github.com/curl/curl/issues/17222) # Schannel ## Extend support for client certificate authentication The existing support for the `-E`/`--cert` and `--key` options could be extended by supplying a custom certificate and key in PEM format, see: [Getting a Certificate for Schannel](https://learn.microsoft.com/windows/win32/secauthn/getting-a-certificate-for-schannel) ## Extend support for the `--ciphers` option The existing support for the `--ciphers` option could be extended by mapping the OpenSSL/GnuTLS cipher suites to the Schannel APIs, see [Specifying Schannel Ciphers and Cipher Strengths](https://learn.microsoft.com/windows/win32/secauthn/specifying-schannel-ciphers-and-cipher-strengths). ## Add option to allow abrupt server closure libcurl with Schannel errors without a known termination point from the server (such as length of transfer, or SSL "close notify" alert) to prevent against a truncation attack. Really old servers may neglect to send any termination point. An option could be added to ignore such abrupt closures. [curl issue 4427](https://github.com/curl/curl/issues/4427) # SASL ## Other authentication mechanisms Add support for other authentication mechanisms such as `OLP`, `GSS-SPNEGO` and others. ## Add `QOP` support to GSSAPI authentication Currently the GSSAPI authentication only supports the default `QOP` of auth (Authentication), whilst Kerberos V5 supports both `auth-int` (Authentication with integrity protection) and `auth-conf` (Authentication with integrity and privacy protection). # SSH protocols ## Multiplexing SSH is a perfectly fine multiplexed protocols which would allow libcurl to do multiple parallel transfers from the same host using the same connection, much in the same spirit as HTTP/2 does. libcurl however does not take advantage of that ability but does instead always create a new connection for new transfers even if an existing connection already exists to the host. To fix this, libcurl would have to detect an existing connection and "attach" the new transfer to the existing one. ## Handle growing SFTP files The SFTP code in libcurl checks the file size *before* a transfer starts and then proceeds to transfer exactly that amount of data. If the remote file grows while the transfer is in progress libcurl does not notice and does not adapt. The OpenSSH SFTP command line tool does and libcurl could also attempt to download more to see if there is more to get... [curl issue 4344](https://github.com/curl/curl/issues/4344) ## Read keys from `~/.ssh/id_ecdsa`, `id_ed25519` The libssh2 backend in curl is limited to only reading keys from `id_rsa` and `id_dsa`, which makes it fail connecting to servers that use more modern key types. [curl issue 8586](https://github.com/curl/curl/issues/8586) ## Support `CURLOPT_PREQUOTE` The two other `QUOTE` options are supported for SFTP, but this was left out for unknown reasons. ## SSH over HTTPS proxy for libssh The SSH based protocols SFTP and SCP did not work over HTTPS proxy at all until [curl pull request 6021](https://github.com/curl/curl/pull/6021) brought the functionality with the libssh2 backend. Presumably, this support can/could be added for the libssh backend as well. ## SFTP with `scp://` OpenSSH 9 switched their `scp` tool to speak SFTP under the hood. Going forward it might be worth having curl or libcurl attempt SFTP if SCP fails to follow suite. # Command line tool ## multi-threading When asked to do transfers in parallel, the curl tool could be extended to use a number of independent worker threads. This would allow faster transfers in situations where curl becomes CPU bound. Ideally, curl would (with permission) fire up new threads on demand when it deems that it might be helpful. Perhaps, if it has more transfers to add and the existing transfers make the CPU busy enough and there are more cores available. ## sync `curl --sync http://example.com/feed[1-100].rss` or `curl --sync http://example.net/{index,calendar,history}.html` Downloads a range or set of URLs using the remote name, but only if the remote file is newer than the local file. A `Last-Modified` HTTP date header should also be used to set the mod date on the downloaded file. ## glob posts Globbing support for `-d` and `-F`, as in `curl -d "name=foo[0-9]" URL`. This is easily scripted though. ## `--proxycommand` Allow the user to make curl run a command and use its stdio to make requests and not do any network connection by itself. Example: curl --proxycommand 'ssh pi@raspberrypi.local -W 10.1.1.75 80' \ http://some/otherwise/unavailable/service.php See [curl issue 4941](https://github.com/curl/curl/issues/4941) ## UTF-8 filenames in Content-Disposition RFC 6266 documents how UTF-8 names can be passed to a client in the `Content-Disposition` header, and curl does not support this. [curl issue 1888](https://github.com/curl/curl/issues/1888) ## Option to make `-Z` merge lined based outputs on stdout When a user requests multiple lined based files using `-Z` and sends them to stdout, curl does not *merge* and send complete lines fine but may send partial lines from several sources. [curl issue 5175](https://github.com/curl/curl/issues/5175) ## specify which response codes that make `-f`/`--fail` return error Allows a user to better specify exactly which error code(s) that are fine and which are errors for their specific uses cases ## Choose the name of file in braces for complex URLs When using braces to download a list of URLs and you use complicated names in the list of alternatives, it could be handy to allow curl to use other names when saving. Consider a way to offer that. Possibly like `{partURL1:name1,partURL2:name2,partURL3:name3}` where the name following the colon is the output name. See [curl issue 221](https://github.com/curl/curl/issues/221) ## improve how curl works in a Windows console window If you pull the scroll bar when transferring with curl in a Windows console window, the transfer is interrupted and can get disconnected. This can probably be improved. See [curl issue 322](https://github.com/curl/curl/issues/322) ## Windows: set attribute 'archive' for completed downloads The archive bit (`FILE_ATTRIBUTE_ARCHIVE, 0x20`) separates files that shall be backed up from those that are either not ready or have not changed. Downloads in progress are neither ready to be backed up, nor should they be opened by a different process. Only after a download has been completed it is sensible to include it in any integer snapshot or backup of the system. See [curl issue 3354](https://github.com/curl/curl/issues/3354) ## keep running, read instructions from pipe/socket Provide an option that makes curl not exit after the last URL (or even work without a given URL), and then make it read instructions passed on a pipe or over a socket to make further instructions so that a second subsequent curl invoke can talk to the still running instance and ask for transfers to get done, and thus maintain its connection pool, DNS cache and more. ## Acknowledge `Ratelimit` headers Consider a command line option that can make curl do multiple serial requests while acknowledging server specified [rate limits](https://datatracker.ietf.org/doc/html/draft-ietf-httpapi-ratelimit-headers/). See [curl issue 5406](https://github.com/curl/curl/issues/5406) ## `--dry-run` A command line option that makes curl show exactly what it would do and send if it would run for real. See [curl issue 5426](https://github.com/curl/curl/issues/5426) ## `--retry` should resume When `--retry` is used and curl actually retries transfer, it should use the already transferred data and do a resumed transfer for the rest (when possible) so that it does not have to transfer the same data again that was already transferred before the retry. See [curl issue 1084](https://github.com/curl/curl/issues/1084) ## retry on network is unreachable The `--retry` option retries transfers on *transient failures*. We later added `--retry-connrefused` to also retry for *connection refused* errors. Suggestions have been brought to also allow retry on *network is unreachable* errors and while totally reasonable, maybe we should consider a way to make this more configurable than to add a new option for every new error people want to retry for? [curl issue 1603](https://github.com/curl/curl/issues/1603) ## hostname sections in config files config files would be more powerful if they could set different configurations depending on used URLs, hostname or possibly origin. Then a default `.curlrc` could a specific user-agent only when doing requests against a certain site. ## retry on the redirected-to URL When curl is told to `--retry` a failed transfer and follows redirects, it might get an HTTP 429 response from the redirected-to URL and not the original one, which then could make curl decide to rather retry the transfer on that URL only instead of the original operation to the original URL. Perhaps extra emphasized if the original transfer is a large POST that redirects to a separate GET, and that GET is what gets the 529 See [curl issue 5462](https://github.com/curl/curl/issues/5462) ## Set the modification date on an uploaded file For SFTP and possibly FTP, curl could offer an option to set the modification time for the uploaded file. See [curl issue 5768](https://github.com/curl/curl/issues/5768) ## Use multiple parallel transfers for a single download To enhance transfer speed, downloading a single URL can be split up into multiple separate range downloads that get combined into a single final result. An ideal implementation would not use a specified number of parallel transfers, but curl could: - First start getting the full file as transfer A - If after N seconds have passed and the transfer is expected to continue for M seconds or more, add a new transfer (B) that asks for the second half of A's content (and stop A at the middle). - If splitting up the work improves the transfer rate, it could then be done again. Then again, etc up to a limit. This way, if transfer B fails (because Range: is not supported) it lets transfer A remain the single one. N and M could be set to some sensible defaults. See [curl issue 5774](https://github.com/curl/curl/issues/5774) ## Prevent terminal injection when writing to terminal curl could offer an option to make escape sequence either non-functional or avoid cursor moves or similar to reduce the risk of a user getting tricked by clever tricks. See [curl issue 6150](https://github.com/curl/curl/issues/6150) ## `-J` and `-O` with %-encoded filenames `-J`/`--remote-header-name` does not decode %-encoded filenames. RFC 6266 details how it should be done. The can of worm is that we have no charset handling in curl and ASCII >=128 is a challenge for us. Not to mention that decoding also means that we need to check for nastiness that is attempted, like `../` sequences and the like. Probably everything to the left of any embedded slashes should be cut off. See https://curl.se/bug/view.cgi?id=1294 `-O` also does not decode %-encoded names, and while it has even less information about the charset involved the process is similar to the `-J` case. Note that we do not decode `-O` without the user asking for it with some other means, since `-O` has always been documented to use the name exactly as specified in the URL. ## `-J` with `-C -` When using `-J` (with `-O`), automatically resumed downloading together with `-C -` fails. Without `-J` the same command line works. This happens because the resume logic is worked out before the target filename (and thus its pre-transfer size) has been figured out. This can be improved. https://curl.se/bug/view.cgi?id=1169 ## `--retry` and transfer timeouts If using `--retry` and the transfer timeouts (possibly due to using -m or `-y`/`-Y`) the next attempt does not resume the transfer properly from what was downloaded in the previous attempt but truncates and restarts at the original position where it was at before the previous failed attempt. See https://curl.se/mail/lib-2008-01/0080.html # Build ## Enable `PIE` and `RELRO` by default Especially when having programs that execute curl via the command line, `PIE` renders the exploitation of memory corruption vulnerabilities a lot more difficult. This can be attributed to the additional information leaks being required to conduct a successful attack. `RELRO`, on the other hand, masks different binary sections like the `GOT` as read-only and thus kills a handful of techniques that come in handy when attackers are able to arbitrarily overwrite memory. A few tests showed that enabling these features had close to no impact, neither on the performance nor on the general functionality of curl. ## Do not use GNU libtool on OpenBSD When compiling curl on OpenBSD with `--enable-debug` it gives linking errors when you use GNU libtool. This can be fixed by using the libtool provided by OpenBSD itself. However for this the user always needs to invoke make with `LIBTOOL=/usr/bin/libtool`. It would be nice if the script could have some logic to detect if this system is an OpenBSD host and then use the OpenBSD libtool instead. See [curl issue 5862](https://github.com/curl/curl/issues/5862) ## Package curl for Windows in a signed installer See [curl issue 5424](https://github.com/curl/curl/issues/5424) ## make configure use `--cache-file` more and better The configure script can be improved to cache more values so that repeated invokes run much faster. See [curl issue 7753](https://github.com/curl/curl/issues/7753) # Test suite ## SSL tunnel Make our own version of stunnel for simple port forwarding to enable HTTPS and FTP-SSL tests without the stunnel dependency, and it could allow us to provide test tools built with either OpenSSL or GnuTLS ## more protocols supported Extend the test suite to include more protocols. The telnet could do FTP or http operations (for which we have test servers). ## more platforms supported Make the test suite work on more platforms. OpenBSD and macOS. Remove fork()s and it should become even more portable. ## write an SMB test server to replace impacket This would allow us to run SMB tests on more platforms and do better and more covering tests. See [curl issue 15697](https://github.com/curl/curl/issues/15697) ## Use the RFC 6265 test suite A test suite made for HTTP cookies (RFC 6265) by Adam Barth [is available](https://github.com/abarth/http-state/tree/master/tests). It would be good if someone would write a script/setup that would run curl with that test suite and detect deviance. Ideally, that would even be incorporated into our regular test suite. ## Run web-platform-tests URL tests Run web-platform-tests URL tests and compare results with browsers on `wpt.fyi`. It would help us find issues to fix and help us document where our parser differs from the WHATWG URL spec parsers. See [curl issue 4477](https://github.com/curl/curl/issues/4477) # MQTT ## Support rate-limiting The rate-limiting logic is done in the PERFORMING state in multi.c but MQTT is not (yet) implemented to use that. ## Support MQTTS ## Handle network blocks Running test suite with `CURL_DBG_SOCK_WBLOCK=90 ./runtests.pl -a mqtt` makes several MQTT test cases fail where they should not. ## large payloads libcurl unnecessarily allocates heap memory to hold the entire payload to get sent, when the data is already perfectly accessible where it is when `CURLOPT_POSTFIELDS` is used. This is highly inefficient for larger payloads. Additionally, libcurl does not support using the read callback for sending MQTT which is yet another way to avoid having to hold large payload in memory. # TFTP ## TFTP does not convert LF to CRLF for `mode=netascii` RFC 3617 defines that an TFTP transfer can be done using `netascii` mode. curl does not support extracting that mode from the URL nor does it treat such transfers specifically. It should probably do LF to CRLF translations for them. See [curl issue 12655](https://github.com/curl/curl/issues/12655) # Gopher ## Handle network blocks Running test suite with `CURL_DBG_SOCK_WBLOCK=90 ./runtests.pl -a 1200 to 1300` makes several Gopher test cases fail where they should not. usr/share/doc/alt-curlssl11/CHANGES.md 0000644 00000000665 15233257620 0013241 0 ustar 00 <!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. SPDX-License-Identifier: curl --> In a release tarball, check the RELEASE-NOTES file for what was done in the most recent release. In a git check-out, that file mentions changes that have been done since the previous release. See the online [changelog](https://curl.se/changes.html) for the edited and human readable version of what has changed in different curl releases. usr/share/doc/alt-curlssl11/COPYING 0000644 00000002100 15233257620 0012664 0 ustar 00 COPYRIGHT AND PERMISSION NOTICE Copyright (c) 1996 - 2026, Daniel Stenberg, <daniel@haxx.se>, and many contributors, see the THANKS file. All rights reserved. Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Except as contained in this notice, the name of a copyright holder shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization of the copyright holder. usr/share/doc/alt-curlssl11/README 0000644 00000002702 15233257620 0012521 0 ustar 00 _ _ ____ _ ___| | | | _ \| | / __| | | | |_) | | | (__| |_| | _ <| |___ \___|\___/|_| \_\_____| README Curl is a command line tool for transferring data specified with URL syntax. Find out how to use curl by reading the curl.1 man page or the MANUAL document. Find out how to install Curl by reading the INSTALL document. libcurl is the library curl is using to do its job. It is readily available to be used by your software. Read the libcurl.3 man page to learn how. You find answers to the most frequent questions we get in the FAQ.md document. Study the COPYING file for distribution terms. Those documents and more can be found in the docs/ directory. CONTACT If you have problems, questions, ideas or suggestions, please contact us by posting to a suitable mailing list. See https://curl.se/mail/ All contributors to the project are listed in the THANKS document. WEBSITE Visit the curl website for the latest news and downloads: https://curl.se/ GIT To download the latest source code off the GIT server, do this: git clone https://github.com/curl/curl (you will get a directory named curl created, filled with the source code) SECURITY PROBLEMS Report suspected security problems privately and not in public. https://curl.se/dev/vuln-disclosure.html usr/share/doc/alt-curlssl11/TheArtOfHttpScripting.md 0000644 00000067042 15233257620 0016372 0 ustar 00 <!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. SPDX-License-Identifier: curl --> # The Art Of Scripting HTTP Requests Using curl ## Background This document assumes that you are familiar with HTML and general networking. The increasing amount of applications moving to the web has made "HTTP Scripting" more frequently requested and wanted. To be able to automatically extract information from the web, to fake users, to post or upload data to web servers are all important tasks today. curl is a command line tool for doing all sorts of URL manipulations and transfers, but this particular document focuses on how to use it when doing HTTP requests for fun and profit. This documents assumes that you know how to invoke `curl --help` or `curl --manual` to get basic information about it. curl is not written to do everything for you. It makes the requests, it gets the data, it sends data and it retrieves the information. You probably need to glue everything together using some kind of script language or repeated manual invokes. ## The HTTP Protocol HTTP is the protocol used to fetch data from web servers. It is a simple protocol that is built upon TCP/IP. The protocol also allows information to get sent to the server from the client using a few different methods, as is shown here. HTTP is plain ASCII text lines being sent by the client to a server to request a particular action, and then the server replies a few text lines before the actual requested content is sent to the client. The client, curl, sends an HTTP request. The request contains a method (like GET, POST, HEAD etc), a number of request headers and sometimes a request body. The HTTP server responds with a status line (indicating if things went well), response headers and most often also a response body. The "body" part is the plain data you requested, like the actual HTML or the image etc. ## See the Protocol Using curl's option [`--verbose`](https://curl.se/docs/manpage.html#-v) (`-v` as a short option) displays what kind of commands curl sends to the server, as well as a few other informational texts. `--verbose` is the single most useful option when it comes to debug or even understand the curl<->server interaction. Sometimes even `--verbose` is not enough. Then [`--trace`](https://curl.se/docs/manpage.html#-trace) and [`--trace-ascii`](https://curl.se/docs/manpage.html#--trace-ascii) offer even more details as they show **everything** curl sends and receives. Use it like this: curl --trace-ascii debugdump.txt https://www.example.com/ ## See the Timing Many times you may wonder what exactly is taking all the time, or you want to know the amount of milliseconds between two points in a transfer. For those, and other similar situations, the [`--trace-time`](https://curl.se/docs/manpage.html#--trace-time) option is what you need. It prepends the time to each trace output line: curl --trace-ascii d.txt --trace-time https://example.com/ ## See which Transfer When doing parallel transfers, it is relevant to see which transfer is doing what. When response headers are received (and logged) you need to know which transfer these are for. [`--trace-ids`](https://curl.se/docs/manpage.html#--trace-ids) option is what you need. It prepends the transfer and connection identifier to each trace output line: curl --trace-ascii d.txt --trace-ids https://example.com/ ## See the Response By default curl sends the response to stdout. You need to redirect it somewhere to avoid that, most often that is done with `-o` or `-O`. # URL ## Spec The Uniform Resource Locator format is how you specify the address of a particular resource on the Internet. You know these, you have seen URLs like https://curl.se/ or https://example.com/ a million times. RFC 3986 is the canonical spec. The formal name is not URL, it is **URI**. ## Host The hostname is usually resolved using DNS or your /etc/hosts file to an IP address and that is what curl communicates with. Alternatively you specify the IP address directly in the URL instead of a name. For development and other trying out situations, you can point to a different IP address for a hostname than what would otherwise be used, by using curl's [`--resolve`](https://curl.se/docs/manpage.html#--resolve) option: curl --resolve www.example.org:80:127.0.0.1 https://www.example.org/ ## Port number Each protocol curl supports operates on a default port number, be it over TCP or in some cases UDP. Normally you do not have to take that into consideration, but at times you run test servers on other ports or similar. Then you can specify the port number in the URL with a colon and a number immediately following the hostname. Like when doing HTTP to port 1234: curl https://www.example.org:1234/ The port number you specify in the URL is the number that the server uses to offer its services. Sometimes you may use a proxy, and then you may need to specify that proxy's port number separately from what curl needs to connect to the server. Like when using an HTTP proxy on port 4321: curl --proxy http://proxy.example.org:4321 https://remote.example.org/ ## Username and password Some services are setup to require HTTP authentication and then you need to provide name and password which is then transferred to the remote site in various ways depending on the exact authentication protocol used. You can opt to either insert the user and password in the URL or you can provide them separately: curl https://user:password@example.org/ or curl -u user:password https://example.org/ You need to pay attention that this kind of HTTP authentication is not what is usually done and requested by user-oriented websites these days. They tend to use forms and cookies instead. ## Path part The path part is sent off to the server to request that it sends back the associated response. The path is what is to the right side of the slash that follows the hostname and possibly port number. # Fetch a page ## GET The simplest and most common request/operation made using HTTP is to GET a URL. The URL could itself refer to a webpage, an image or a file. The client issues a GET request to the server and receives the document it asked for. If you issue the command line curl https://curl.se/ you get a webpage returned in your terminal window. The entire HTML document this URL identifies. All HTTP replies contain a set of response headers that are normally hidden, use curl's [`--include`](https://curl.se/docs/manpage.html#-i) (`-i`) option to display them as well as the rest of the document. ## HEAD You can ask the remote server for ONLY the headers by using the [`--head`](https://curl.se/docs/manpage.html#-I) (`-I`) option which makes curl issue a HEAD request. In some special cases servers deny the HEAD method while others still work, which is a particular kind of annoyance. The HEAD method is defined and made so that the server returns the headers exactly the way it would do for a GET, but without a body. It means that you may see a `Content-Length:` in the response headers, but there must not be an actual body in the HEAD response. ## Multiple URLs in a single command line A single curl command line may involve one or many URLs. The most common case is probably to use one, but you can specify any amount of URLs. Yes any. No limits. You then get requests repeated over and over for all the given URLs. Example, send two GET requests: curl https://url1.example.com https://url2.example.com If you use [`--data`](https://curl.se/docs/manpage.html#-d) to POST to the URL, using multiple URLs means that you send that same POST to all the given URLs. Example, send two POSTs: curl --data name=curl https://url1.example.com https://url2.example.com ## Multiple HTTP methods in a single command line Sometimes you need to operate on several URLs in a single command line and do different HTTP methods on each. For this, you might enjoy the [`--next`](https://curl.se/docs/manpage.html#-:) option. It is a separator that separates a bunch of options from the next. All the URLs before `--next` get the same method and get all the POST data merged into one. When curl reaches the `--next` on the command line, it resets the method and the POST data and allow a new set. Perhaps this is best shown with a few examples. To send first a HEAD and then a GET: curl -I https://example.com --next https://example.com To first send a POST and then a GET: curl -d score=10 https://example.com/post.cgi --next https://example.com/results.html # HTML forms ## Forms explained Forms are the general way a website can present an HTML page with fields for the user to enter data in, and then press some kind of 'OK' or 'Submit' button to get that data sent to the server. The server then typically uses the posted data to decide how to act. Like using the entered words to search in a database, or to add the info in a bug tracking system, display the entered address on a map or using the info as a login-prompt verifying that the user is allowed to see what it is about to see. Of course there has to be some kind of program on the server end to receive the data you send. You cannot invent something out of the air. ## GET A GET-form uses the method GET, as specified in HTML like: ```html <form method="GET" action="junk.cgi"> <input type=text name="birthyear"> <input type=submit name=press value="OK"> </form> ``` In your favorite browser, this form appears with a text box to fill in and a press-button labeled "OK". If you fill in '1905' and press the OK button, your browser then creates a new URL to get for you. The URL gets `junk.cgi?birthyear=1905&press=OK` appended to the path part of the previous URL. If the original form was seen on the page `www.example.com/when/birth.html`, the second page you get becomes `www.example.com/when/junk.cgi?birthyear=1905&press=OK`. Most search engines work this way. To make curl do the GET form post for you, enter the expected created URL: curl "https://www.example.com/when/junk.cgi?birthyear=1905&press=OK" ## POST The GET method makes all input field names get displayed in the URL field of your browser. That is generally a good thing when you want to be able to bookmark that page with your given data, but it is an obvious disadvantage if you entered secret information in one of the fields or if there are a large amount of fields creating a long and unreadable URL. The HTTP protocol then offers the POST method. This way the client sends the data separated from the URL and thus you do not see any of it in the URL address field. The form would look similar to the previous one: ```html <form method="POST" action="junk.cgi"> <input type=text name="birthyear"> <input type=submit name=press value=" OK "> </form> ``` To use curl to post this form with the same data filled in as before, we could do it like: curl --data "birthyear=1905&press=%20OK%20" https://www.example.com/when/junk.cgi This kind of POST uses the Content-Type `application/x-www-form-urlencoded` and is the most widely used POST kind. The data you send to the server MUST already be properly encoded, curl does not do that for you. For example, if you want the data to contain a space, you need to replace that space with `%20`, etc. Failing to comply with this most likely causes your data to be received wrongly and messed up. Recent curl versions can in fact URL encode POST data for you, like this: curl --data-urlencode "name=I am Daniel" https://www.example.com If you repeat `--data` several times on the command line, curl concatenates all the given data pieces - and put a `&` symbol between each data segment. ## File Upload POST Back in late 1995 they defined an additional way to post data over HTTP. It is documented in the RFC 1867, why this method sometimes is referred to as RFC 1867-posting. This method is mainly designed to better support file uploads. A form that allows a user to upload a file could be written like this in HTML: <form method="POST" enctype='multipart/form-data' action="upload.cgi"> <input name=upload type=file> <input type=submit name=press value="OK"> </form> This clearly shows that the Content-Type about to be sent is `multipart/form-data`. To post to a form like this with curl, you enter a command line like: curl --form upload=@localfilename --form press=OK [URL] ## Hidden Fields A common way for HTML based applications to pass state information between pages is to add hidden fields to the forms. Hidden fields are already filled in, they are not displayed to the user and they get passed along as all the other fields. A similar example form with one visible field, one hidden field and one submit button could look like: ```html <form method="POST" action="foobar.cgi"> <input type=text name="birthyear"> <input type=hidden name="person" value="daniel"> <input type=submit name="press" value="OK"> </form> ``` To POST this with curl, you do not have to think about if the fields are hidden or not. To curl they are all the same: curl --data "birthyear=1905&press=OK&person=daniel" [URL] ## Figure Out What A POST Looks Like When you are about to fill in a form and send it to a server by using curl instead of a browser, you are of course interested in sending a POST exactly the way your browser does. An easy way to get to see this, is to save the HTML page with the form on your local disk, modify the 'method' to a GET, and press the submit button (you could also change the action URL if you want to). You then clearly see the data get appended to the URL, separated with a `?`-letter as GET forms are supposed to. # HTTP upload ## PUT Perhaps the best way to upload data to an HTTP server is to use PUT. Then again, this of course requires that someone put a program or script on the server end that knows how to receive an HTTP PUT stream. Put a file to an HTTP server with curl: curl --upload-file uploadfile https://www.example.com/receive.cgi # HTTP Authentication ## Basic Authentication HTTP Authentication is the ability to tell the server your username and password so that it can verify that you are allowed to do the request you are doing. The Basic authentication used in HTTP (which is the type curl uses by default) is **plain text** based, which means it sends username and password only slightly obfuscated, but still fully readable by anyone that sniffs on the network between you and the remote server. To tell curl to use a user and password for authentication: curl --user myname:password https://www.example.com ## Other Authentication The site might require a different authentication method (check the headers returned by the server), and then [`--ntlm`](https://curl.se/docs/manpage.html#--ntlm), [`--digest`](https://curl.se/docs/manpage.html#--digest), [`--negotiate`](https://curl.se/docs/manpage.html#--negotiate) or even [`--anyauth`](https://curl.se/docs/manpage.html#--anyauth) might be options that suit you. ## Proxy Authentication Sometimes your HTTP access is only available through the use of an HTTP proxy. This seems to be especially common at various companies. An HTTP proxy may require its own user and password to allow the client to get through to the Internet. To specify those with curl, run something like: curl --proxy-user proxyuser:proxypassword curl.se If your proxy requires the authentication to be done using the NTLM method, use [`--proxy-ntlm`](https://curl.se/docs/manpage.html#--proxy-ntlm), if it requires Digest use [`--proxy-digest`](https://curl.se/docs/manpage.html#--proxy-digest). If you use any one of these user+password options but leave out the password part, curl prompts for the password interactively. ## Hiding credentials Do note that when a program is run, its parameters might be possible to see when listing the running processes of the system. Thus, other users may be able to watch your passwords if you pass them as plain command line options. There are ways to circumvent this. It is worth noting that while this is how HTTP Authentication works, many websites do not use this concept when they provide logins etc. See the Web Login chapter further below for more details on that. # More HTTP Headers ## Referer An HTTP request may include a 'referer' field (yes it is misspelled), which can be used to tell from which URL the client got to this particular resource. Some programs/scripts check the referer field of requests to verify that this was not arriving from an external site or an unknown page. While this is a stupid way to check something so easily forged, many scripts still do it. Using curl, you can put anything you want in the referer-field and thus more easily be able to fool the server into serving your request. Use curl to set the referer field with: curl --referer https://www.example.come https://www.example.com ## User Agent Similar to the referer field, all HTTP requests may set the User-Agent field. It names what user agent (client) that is being used. Many applications use this information to decide how to display pages. Silly web programmers try to make different pages for users of different browsers to make them look the best possible for their particular browsers. They usually also do different kinds of JavaScript etc. At times, you may learn that getting a page with curl does not return the same page that you see when getting the page with your browser. Then you know it is time to set the User Agent field to fool the server into thinking you are one of those browsers. By default, curl uses curl/VERSION, such as User-Agent: curl/8.11.0. To make curl look like Internet Explorer 5 on a Windows 2000 box: curl --user-agent "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)" [URL] Or why not look like you are using Netscape 4.73 on an old Linux box: curl --user-agent "Mozilla/4.73 [en] (X11; U; Linux 2.2.15 i686)" [URL] ## Redirects ## Location header When a resource is requested from a server, the reply from the server may include a hint about where the browser should go next to find this page, or a new page keeping newly generated output. The header that tells the browser to redirect is `Location:`. curl does not follow `Location:` headers by default, but displays such pages in the same manner it displays all HTTP replies. It does however feature an option that makes it attempt to follow the `Location:` pointers. To tell curl to follow a Location: curl --location https://www.example.com If you use curl to POST to a site that immediately redirects you to another page, you can safely use [`--location`](https://curl.se/docs/manpage.html#-L) (`-L`) and `--data`/`--form` together. curl only uses POST in the first request, and then revert to GET in the following operations. ## Other redirects Browsers typically support at least two other ways of redirects that curl does not: first the html may contain a meta refresh tag that asks the browser to load a specific URL after a set number of seconds, or it may use JavaScript to do it. # Cookies ## Cookie Basics The way the web browsers do "client side state control" is by using cookies. Cookies are names with associated contents. The cookies are sent to the client by the server. The server tells the client for what path and hostname it wants the cookie sent back, and it also sends an expiration date and a few more properties. When a client communicates with a server with a name and path as previously specified in a received cookie, the client sends back the cookies and their contents to the server, unless of course they are expired. Many applications and servers use this method to connect a series of requests into a single logical session. To be able to use curl in such occasions, we must be able to record and send back cookies the way the web application expects them. The same way browsers deal with them. ## Cookie options The simplest way to send a few cookies to the server when getting a page with curl is to add them on the command line like: curl --cookie "name=Daniel" https://www.example.com Cookies are sent as common HTTP headers. This is practical as it allows curl to record cookies by recording headers. Record cookies with curl by using the [`--dump-header`](https://curl.se/docs/manpage.html#-D) (`-D`) option like: curl --dump-header headers_and_cookies https://www.example.com (Take note that the [`--cookie-jar`](https://curl.se/docs/manpage.html#-c) option described below is a better way to store cookies.) curl has a full blown cookie parsing engine built-in that comes in use if you want to reconnect to a server and use cookies that were stored from a previous connection (or hand-crafted manually to fool the server into believing you had a previous connection). To use previously stored cookies, you run curl like: curl --cookie stored_cookies_in_file https://www.example.com curl's "cookie engine" gets enabled when you use the [`--cookie`](https://curl.se/docs/manpage.html#-b) option. If you only want curl to understand received cookies, use `--cookie` with a file that does not exist. Example, if you want to let curl understand cookies from a page and follow a location (and thus possibly send back cookies it received), you can invoke it like: curl --cookie nada --location https://www.example.com curl has the ability to read and write cookie files that use the same file format that Netscape and Mozilla once used. It is a convenient way to share cookies between scripts or invokes. The `--cookie` (`-b`) switch automatically detects if a given file is such a cookie file and parses it, and by using the `--cookie-jar` (`-c`) option you make curl write a new cookie file at the end of an operation: curl --cookie cookies.txt --cookie-jar newcookies.txt \ https://www.example.com # HTTPS ## HTTPS is HTTP secure There are a few ways to do secure HTTP transfers. By far the most common protocol for doing this is what is generally known as HTTPS, HTTP over SSL. SSL encrypts all the data that is sent and received over the network and thus makes it harder for attackers to spy on sensitive information. SSL (or TLS as the current version of the standard is called) offers a set of advanced features to do secure transfers over HTTP. curl supports encrypted fetches when built to use a TLS library and it can be built to use one out of a fairly large set of libraries - `curl -V` shows which one your curl was built to use (if any). To get a page from an HTTPS server, run curl like: curl https://secure.example.com ## Certificates In the HTTPS world, you use certificates to validate that you are the one you claim to be, as an addition to normal passwords. curl supports client- side certificates. All certificates are locked with a passphrase, which you need to enter before the certificate can be used by curl. The passphrase can be specified on the command line or if not, entered interactively when curl queries for it. Use a certificate with curl on an HTTPS server like: curl --cert mycert.pem https://secure.example.com curl also tries to verify that the server is who it claims to be, by verifying the server's certificate against a locally stored CA cert bundle. Failing the verification causes curl to deny the connection. You must then use [`--insecure`](https://curl.se/docs/manpage.html#-k) (`-k`) in case you want to tell curl to ignore that the server cannot be verified. More about server certificate verification and CA cert bundles can be read in the [`SSLCERTS` document](https://curl.se/docs/sslcerts.html). At times you may end up with your own CA cert store and then you can tell curl to use that to verify the server's certificate: curl --cacert ca-bundle.pem https://example.com/ # Custom Request Elements ## Modify method and headers Doing fancy stuff, you may need to add or change elements of a single curl request. For example, you can change the POST method to `PROPFIND` and send the data as `Content-Type: text/xml` (instead of the default `Content-Type`) like this: curl --data "<xml>" --header "Content-Type: text/xml" \ --request PROPFIND example.com You can delete a default header by providing one without content. Like you can ruin the request by chopping off the `Host:` header: curl --header "Host:" https://www.example.com You can add headers the same way. Your server may want a `Destination:` header, and you can add it: curl --header "Destination: nowhere" https://example.com ## More on changed methods It should be noted that curl selects which methods to use on its own depending on what action to ask for. `-d` makes a POST, `-I` makes a HEAD and so on. If you use the [`--request`](https://curl.se/docs/manpage.html#-X) / `-X` option you can change the method keyword curl selects, but you do not modify curl's behavior. This means that if you for example use -d "data" to do a POST, you can modify the method to a `PROPFIND` with `-X` and curl still thinks it sends a POST. You can change the normal GET to a POST method by adding `-X POST` in a command line like: curl -X POST https://example.org/ curl however still acts as if it sent a GET so it does not send any request body etc. # Web Login ## Some login tricks While not strictly HTTP related, it still causes a lot of people problems so here's the executive run-down of how the vast majority of all login forms work and how to login to them using curl. It can also be noted that to do this properly in an automated fashion, you most certainly need to script things and do multiple curl invokes etc. First, servers mostly use cookies to track the logged-in status of the client, so you need to capture the cookies you receive in the responses. Then, many sites also set a special cookie on the login page (to make sure you got there through their login page) so you should make a habit of first getting the login-form page to capture the cookies set there. Some web-based login systems feature various amounts of JavaScript, and sometimes they use such code to set or modify cookie contents. Possibly they do that to prevent programmed logins, like this manual describes how to... Anyway, if reading the code is not enough to let you repeat the behavior manually, capturing the HTTP requests done by your browsers and analyzing the sent cookies is usually a working method to work out how to shortcut the JavaScript need. In the actual `<form>` tag for the login, lots of sites fill-in random/session or otherwise secretly generated hidden tags and you may need to first capture the HTML code for the login form and extract all the hidden fields to be able to do a proper login POST. Remember that the contents need to be URL encoded when sent in a normal POST. # Debug ## Some debug tricks Many times when you run curl on a site, you notice that the site does not seem to respond the same way to your curl requests as it does to your browser's. Then you need to start making your curl requests more similar to your browser's requests: - Use the `--trace-ascii` option to store fully detailed logs of the requests for easier analyzing and better understanding - Make sure you check for and use cookies when needed (both reading with `--cookie` and writing with `--cookie-jar`) - Set user-agent (with [`-A`](https://curl.se/docs/manpage.html#-A)) to one like a recent popular browser does - Set referer (with [`-E`](https://curl.se/docs/manpage.html#-E)) like it is set by the browser - If you use POST, make sure you send all the fields and in the same order as the browser does it. ## Check what the browsers do A good helper to make sure you do this right, is the web browsers' developers tools that let you view all headers you send and receive (even when using HTTPS). A more raw approach is to capture the HTTP traffic on the network with tools such as Wireshark or tcpdump and check what headers that were sent and received by the browser. (HTTPS forces you to use `SSLKEYLOGFILE` to do that.) usr/share/doc/alt-curlssl11/BUGS.md 0000644 00000026723 15233257620 0012734 0 ustar 00 <!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. SPDX-License-Identifier: curl --> # BUGS ## There are still bugs curl and libcurl keep being developed. Adding features and changing code means that bugs sneak in, no matter how hard we try to keep them out. Of course there are lots of bugs left. Not to mention misfeatures. To help us make curl the stable and solid product we want it to be, we need bug reports and bug fixes. ## Where to report If you cannot fix a bug yourself and submit a fix for it, try to report an as detailed report as possible to a curl mailing list to allow one of us to have a go at a solution. You can optionally also submit your problem in [curl's bug tracking system](https://github.com/curl/curl/issues). Please read the rest of this document below first before doing that. If you feel you need to ask around first, find a suitable [mailing list](https://curl.se/mail/) and post your questions there. ## Security bugs If you find a bug or problem in curl or libcurl that you think has a security impact, for example a bug that can put users in danger or make them vulnerable if the bug becomes public knowledge, then please report that bug using our security development process. Security related bugs or bugs that are suspected to have a security impact, should be reported [privately](https://curl.se/dev/vuln-disclosure.html). This ensures that the report reaches the curl security team so that they first can deal with the report away from the public to minimize the harm and impact it has on existing users out there who might be using the vulnerable versions. The curl project's process for handling security related issues is [documented separately](https://curl.se/dev/secprocess.html). ## What to report When reporting a bug, you should include all information to help us understand what is wrong, what you expected to happen and how to repeat the bad behavior. You therefore need to tell us: - your operating system's name and version number - what version of curl you are using (`curl -V` is fine) - versions of the used libraries that libcurl is built to use - what URL you were working with (if possible), at least which protocol and anything and everything else you think matters. Tell us what you expected to happen, tell us what did happen, tell us how you could make it work another way. Dig around, try out, test. Then include all the tiny bits and pieces in your report. You benefit from this yourself, as it enables us to help you quicker and more accurately. Since curl deals with networks, it often helps us if you include a protocol debug dump with your bug report. The output you get by using the `-v` or `--trace` options. If curl crashed, causing a core dump (in Unix), there is hardly any use to send that huge file to anyone of us. Unless we have the same system setup as you, we cannot do much with it. Instead, we ask you to get a stack trace and send that (much smaller) output to us instead. The address and how to subscribe to the mailing lists are detailed in the `MANUAL.md` file. ## libcurl problems When you have written your own application with libcurl to perform transfers, it is even more important to be specific and detailed when reporting bugs. Tell us the libcurl version and your operating system. Tell us the name and version of all relevant sub-components like for example the SSL library you are using and what name resolving your libcurl uses. If you use SFTP or SCP, the libssh2 version is relevant etc. Showing us a real source code example repeating your problem is the best way to get our attention and it greatly increases our chances to understand your problem and to work on a fix (if we agree it truly is a problem). Lots of problems that appear to be libcurl problems are instead abuses of the libcurl API or other malfunctions in your applications. It is advised that you run your problematic program using a memory debug tool like valgrind or similar before you post memory-related or "crashing" problems to us. ## Who fixes the problems If the problems or bugs you describe are considered to be bugs, we want to have the problems fixed. There are no developers in the curl project that are paid to work on bugs. All developers that take on reported bugs do this on a voluntary basis. We do it out of an ambition to keep curl and libcurl excellent products and out of pride. Please do not assume that you can lump over something to us and it then automatically gets fixed after some given time. Most often we need feedback and help to understand what you have experienced and how to repeat a problem. Then we may only be able to assist YOU to debug the problem and to track down the proper fix. We get reports from many people every month and each report can take a considerable amount of time to really go to the bottom with. ## How to get a stack trace First, you must make sure that you compile all sources with `-g` and that you do not 'strip' the final executable. Try to avoid optimizing the code as well, remove `-O`, `-O2` etc from the compiler options. Run the program until it cores. Run your debugger on the core file, like `<debugger> curl core`. `<debugger>` should be replaced with the name of your debugger, in most cases that is `gdb`, but `dbx` and others also occur. When the debugger has finished loading the core file and presents you a prompt, enter `where` (without quotes) and press return. The list that is presented is the stack trace. If everything worked, it is supposed to contain the chain of functions that were called when curl crashed. Include the stack trace with your detailed bug report, it helps a lot. ## Bugs in libcurl bindings There are of course bugs in libcurl bindings. You should then primarily approach the team that works on that particular binding and see what you can do to help them fix the problem. If you suspect that the problem exists in the underlying libcurl, then please convert your program over to plain C and follow the steps outlined above. ## Bugs in old versions The curl project typically releases new versions every other month, and we fix several hundred bugs per year. For a huge table of releases, number of bug fixes and more, see: https://curl.se/docs/releases.html The developers in the curl project do not have bandwidth or energy enough to maintain several branches or to spend much time on hunting down problems in old versions when chances are we already fixed them or at least that they have changed nature and appearance in later versions. When you experience a problem and want to report it, you really SHOULD include the version number of the curl you are using when you experience the issue. If that version number shows us that you are using an out-of-date curl, you should also try out a modern curl version to see if the problem persists or how/if it has changed in appearance. Even if you cannot immediately upgrade your application/system to run the latest curl version, you can most often at least run a test version or experimental build or similar, to get this confirmed or not. At times people insist that they cannot upgrade to a modern curl version, they only "want the bug fixed". That is fine, but do not count on us spending many cycles on trying to identify which single commit, if that is even possible, that at some point in the past fixed the problem you are now experiencing. Security wise, it is almost always a bad idea to lag behind the current curl versions by a lot. We keep discovering and reporting security problems over time see you can see in [this table](https://curl.se/docs/vulnerabilities.html) # Bug fixing procedure ## What happens on first filing When a new issue is posted in the issue tracker or on the mailing list, the team of developers first needs to see the report. Maybe they took the day off, maybe they are off in the woods hunting. Have patience. Allow at least a few days before expecting someone to have responded. In the issue tracker, you can expect that some labels are set on the issue to help categorize it. ## First response If your issue/bug report was not perfect at once (and few are), chances are that someone asks follow-up questions. Which version did you use? Which options did you use? How often does the problem occur? How can we reproduce this problem? Which protocols does it involve? Or perhaps much more specific and deep diving questions. It all depends on your specific issue. You should then respond to these follow-up questions and provide more info about the problem, so that we can help you figure it out. Or maybe you can help us figure it out. An active back-and-forth communication is important and the key for finding a cure and landing a fix. ## Not reproducible We may require further work from you who actually see or experience the problem if we cannot reproduce it and cannot understand it even after having gotten all the info we need and having studied the source code over again. ## Unresponsive If the problem have not been understood or reproduced, and there is nobody responding to follow-up questions or questions asking for clarifications or for discussing possible ways to move forward with the task, we take that as a strong suggestion that the bug is unimportant. Unimportant issues are closed as inactive sooner or later as they cannot be fixed. The inactivity period (waiting for responses) should not be shorter than two weeks but may extend months. ## Lack of time/interest Bugs that are filed and are understood can unfortunately end up in the "nobody cares enough about it to work on it" category. Such bugs are perfectly valid problems that *should* get fixed but apparently are not. We try to mark such bugs as `KNOWN_BUGS material` after a time of inactivity and if no activity is noticed after yet some time those bugs are added to the `KNOWN_BUGS` document and are closed in the issue tracker. ## `KNOWN_BUGS` This is a list of known bugs. Bugs we know exist and that have been pointed out but that have not yet been fixed. The reasons for why they have not been fixed can involve anything really, but the primary reason is that nobody has considered these problems to be important enough to spend the necessary time and effort to have them fixed. The `KNOWN_BUGS` items are always up for grabs and we love the ones who bring one of them back to life and offer solutions to them. The `KNOWN_BUGS` document has a sibling document known as `TODO`. ## `TODO` Issues that are filed or reported that are not really bugs but more missing features or ideas for future improvements and so on are marked as *enhancement* or *feature-request* and get added to the `TODO` document and the issues are closed. We do not keep TODO items open in the issue tracker. The `TODO` document is full of ideas and suggestions of what we can add or fix one day. You are always encouraged and free to grab one of those items and take up a discussion with the curl development team on how that could be implemented or provided in the project so that you can work on ticking it odd that document. If an issue is rather a bug and not a missing feature or functionality, it is listed in `KNOWN_BUGS` instead. ## Closing off stalled bugs The [issue and pull request trackers](https://github.com/curl/curl) only hold "active" entries open (using a non-precise definition of what active actually is, but they are at least not completely dead). Those that are abandoned or in other ways dormant are closed and sometimes added to `TODO` and `KNOWN_BUGS` instead. This way, we only have "active" issues open on GitHub. Irrelevant issues and pull requests do not distract developers or casual visitors. usr/share/man/man1/wcurl.1 0000644 00000010524 15233257620 0011313 0 ustar 00 .\" generated by cd2nroff 0.1 from wcurl.md .TH wcurl 1 "2026-06-30" wcurl .SH NAME \fBwcurl\fP \- a simple wrapper around curl to easily download files. .SH SYNOPSIS \fBwcurl <URL>...\fP \fBwcurl [\--curl\-options <CURL_OPTIONS>]... [\--dry\-run] [\--no\-decode\-filename] [\-o|\-O|\--output <PATH>] [\--] <URL>...\fP \fBwcurl [\--curl\-options=<CURL_OPTIONS>]... [\--dry\-run] [\--no\-decode\-filename] [\--output=<PATH>] [\--] <URL>...\fP \fBwcurl \-V|\--version\fP \fBwcurl \-h|\--help\fP .SH DESCRIPTION \fBwcurl\fP is a simple curl wrapper which lets you use curl to download files without having to remember any parameters. Call \fBwcurl\fP with a list of URLs you want to download and \fBwcurl\fP picks sane defaults. If you need anything more complex, you can provide any of curl\(aqs supported parameters via the \fB\--curl\-options\fP option. Beware that you likely should be using curl directly if your use case is not covered. By default, \fBwcurl\fP does: .IP "* Percent-encode whitespace in URLs;" .IP "* Download multiple URLs in parallel" .nf if the installed curl's version is \>= 7.66.0 (--parallel); .fi .IP "* Use a total number of 5 parallel connections to the same protocol + hostname + port number target" .nf if the installed curl's version is \>= 8.16.0 (--parallel-max-host); .fi .IP "* Follow redirects;" .IP "* Automatically choose a filename as output;" .IP "* Avoid overwriting files" .nf if the installed curl's version is \>= 7.83.0 (--no-clobber); .fi .IP "* Perform retries;" .IP "* Set the downloaded file timestamp" .nf to the value provided by the server, if available; .fi .IP "* Default to https" .nf if the URL does not contain any scheme; .fi .IP "* Disable curl's URL globbing parser" .nf so {} and [] characters in URLs are not treated specially; .fi .IP "* Percent-decode the resulting filename;" .IP "* Use 'index.html' as the default filename" .nf if there is none in the URL. .fi .SH OPTIONS .IP "--curl-options, --curl-options=\<CURL_OPTIONS\>..." Specify extra options to be passed when invoking curl. May be specified more than once. .IP "-o, -O, --output, --output=\<PATH\>" Use the provided output path instead of getting it from the URL. If multiple URLs are provided, resulting files share the same name with a number appended to the end (curl >= 7.83.0). If this option is provided multiple times, only the last value is considered. .IP --no-decode-filename Do not percent\-decode the output filename, even if the percent\-encoding in the URL was done by \fBwcurl\fP, e.g.: The URL contained whitespace. .IP --dry-run Do not actually execute curl, print what would be invoked. .IP "-V, \--version" Print version information. .IP "-h, \--help" Print help message. .SH CURL_OPTIONS Any option supported by curl can be set here. This is not used by \fBwcurl\fP; it is instead forwarded to the curl invocation. .SH URL URL to be downloaded. Anything that is not a parameter is considered an URL. Whitespace is percent\-encoded and the URL is passed to curl, which then performs the parsing. May be specified more than once. .SH EXAMPLES Download a single file: \fBwcurl example.com/filename.txt\fP Download two files in parallel: \fBwcurl example.com/filename1.txt example.com/filename2.txt\fP Download a file passing the \fB\--progress\-bar\fP and \fB\--http2\fP flags to curl: \fBwcurl \--curl\-options="\--progress\-bar \--http2" example.com/filename.txt\fP Resume from an interrupted download. The options necessary to resume the download (\fI\--clobber \--continue\-at \-\fP) must be the \fBlast\fP options specified in \fI\--curl\-options\fP. Note that the only way to resume interrupted downloads is to allow wcurl to overwrite the destination file: \fBwcurl \--curl\-options="\--clobber \--continue\-at \-" example.com/filename.txt\fP Download multiple files without a limit of concurrent connections per host (the default limit is 5): \fBwcurl \--curl\-options="\--parallel\-max\-host 0" example.com/filename1.txt example.com/filename2.txt\fP .SH AUTHORS .nf Samuel Henrique \<samueloph@debian.org\> Sergio Durigan Junior \<sergiodj@debian.org\> and many contributors, see the AUTHORS file. .fi .SH REPORTING BUGS If you experience any problems with \fBwcurl\fP that you do not experience with curl, submit an issue on GitHub: https://github.com/curl/wcurl .SH COPYRIGHT \fBwcurl\fP is licensed under the curl license .SH SEE ALSO .BR curl (1), .BR trurl (1) usr/share/man/man1/curl.1 0000644 00001033620 15233257621 0011130 0 ustar 00 .\" ************************************************************************** .\" * _ _ ____ _ .\" * Project ___| | | | _ \| | .\" * / __| | | | |_) | | .\" * | (__| |_| | _ <| |___ .\" * \___|\___/|_| \_\_____| .\" * .\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. .\" * .\" * This software is licensed as described in the file COPYING, which .\" * you should have received as part of this distribution. The terms .\" * are also available at https://curl.se/docs/copyright.html. .\" * .\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell .\" * copies of the Software, and permit persons to whom the Software is .\" * furnished to do so, under the terms of the COPYING file. .\" * .\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY .\" * KIND, either express or implied. .\" * .\" * SPDX-License-Identifier: curl .\" * .\" ************************************************************************** .\" .\" DO NOT EDIT. Generated by the curl project managen man page generator. .\" .TH curl 1 "2026-06-30" "curl 8.21.0" "curl Manual" .SH NAME curl \- transfer a URL .SH SYNOPSIS \fBcurl [options / URLs]\fP .SH DESCRIPTION \fBcurl\fP is a tool for transferring data from or to a server using URLs. It supports these protocols: DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, MQTTS, POP3, POP3S, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS and WSS. curl is powered by libcurl for all transfer\-related features. See \fIlibcurl(3)\fP for details. .SH URL The URL syntax is protocol\-dependent. You can find a detailed description in RFC 3986. If you provide a URL without a leading "protocol://" scheme, curl guesses what protocol you want. It then defaults to HTTP but assumes others based on often\-used hostname prefixes. For example, for hostnames starting with "ftp." curl assumes you want FTP. You can specify any amount of URLs on the command line. They are fetched in a sequential manner in the specified order unless you use \fI\-\-parallel\fP. You can specify command line options and URLs mixed and in any order on the command line. curl attempts to reuse connections when doing multiple transfers, so that getting many files from the same server do not use multiple connects and setup handshakes. This improves speed. Connection reuse can only be done for URLs specified for a single command line invocation and cannot be performed between separate curl runs. Everything provided on the command line that is not a command line option or its argument, curl assumes is a URL and treats it as such. .SH GLOBBING You can specify multiple URLs or parts of URLs by writing lists within braces or ranges within brackets. We call this "globbing". Provide a list with three different names like this: .nf https://fun.example/{one,two,three}.jpg sftp://{one,two,three}.example/README .fi Do sequences of alphanumeric series by using [] as in: .nf ftp://ftp.example.com/file[1\-100].txt .fi With leading zeroes: .nf ftp://ftp.example.com/file[001\-100].txt .fi With letters through the alphabet: .nf ftp://ftp.example.com/file[a\-z].txt .fi Nested sequences are not supported, but you can use several ones next to each other: .nf https://example.com/archive[1996\-1999]/vol[1\-4]/part{a,b,c}.html .fi You can specify a step counter for the ranges to get every Nth number or letter: .nf https://example.com/file[1\-100:10].txt https://example.com/file[a\-z:2].txt .fi When using [] or {} sequences when invoked from a command line prompt, you probably have to put the full URL within double quotes to avoid the shell from interfering with it. This also goes for other characters treated special, like for example \(aq&\(aq, \(aq?\(aq and \(aq*\(aq. The separate globbing components can be referenced in the \fI\-\-output\fP option to allow pieces to be reused in the target filename. Starting in curl 8.21.0, the separate globbing parts can be named and referenced by their names. The case sensitive alphanumeric name is set enclosed within angle brackets after the opening character. Examples: .nf https://fun.example/{<number>one,two,three}.jpg ftp://ftp.example.com/file[<range>1\-100].txt .fi Setting the same glob name twice is an error. Switch off globbing with \fI\-\-globoff\fP. .SH VARIABLES curl supports command line variables (added in 8.3.0). Set variables with \fI\-\-variable\fP name=content or \fI\-\-variable\fP name@file (where "file" can be stdin if set to a single dash (\-)). Variable contents can be expanded in option parameters using "{{name}}" if the option name is prefixed with "\fI\-\-expand\-\fP". This gets the contents of the variable "name" inserted, or a blank if the name does not exist as a variable. Insert "{{" verbatim in the string by prefixing it with a backslash, like "\\{{". You can access and expand environment variables by importing them with \&"\fI\-\-variable\fP %name". This imports the variable called "name" but exits with an error if that environment variable is not already set. To provide a default value in case it is not already set, use "\fI\-\-variable\fP %name=content" or \&"\fI\-\-variable\fP %name@content". Example: get the USER environment variable and expand into the URL, fail if USER is not set: .nf -\-variable \(aq%USER\(aq -\-expand\-url = "https://example.com/api/{{USER}}/method" .fi When expanding variables, curl supports a set of functions that can make the variable contents more convenient to use. It can trim leading and trailing white space with "trim", output the contents as a JSON quoted string with \&"json", URL encode the string with "url", base64 encode it with "b64" and base64 decode it with "64dec". To apply functions to a variable expansion, add them colon separated to the right side of the variable. Variable content holding null bytes that are not encoded when expanded causes an error. Example: get the contents of a file called $HOME/.secret into a variable called "fix". Make sure that the content is trimmed and percent\-encoded when sent as POST data: .nf -\-variable %HOME -\-expand\-variable fix@{{HOME}}/.secret -\-expand\-data "{{fix:trim:url}}" https://example.com/ .fi Command line variables and expansions were added in 8.3.0. .SH OUTPUT If not told otherwise, curl writes the received data to stdout. It can be instructed to instead save that data into a local file, using the \fI\-\-output\fP or \fI\-\-remote\-name\fP options. If curl is given multiple URLs to transfer on the command line, it similarly needs multiple options for where to save them. curl does not parse or otherwise "understand" the content it gets or writes as output. It does no encoding or decoding, unless explicitly asked to with dedicated command line options. .SH PROTOCOLS curl supports numerous protocols, or put in URL terms: schemes. Your particular build may not support them all. .IP DICT Lets you lookup words using online dictionaries. .IP FILE Read or write local files. curl does not support accessing "file://" URL remotely, but when running on Microsoft Windows using the native UNC approach works. Only absolute paths. .IP FTP(S) curl supports the File Transfer Protocol with a lot of tweaks and levers. With or without using TLS. .IP GOPHER(S) Retrieve files. .IP HTTP(S) curl supports HTTP with numerous options and variations. It can speak HTTP version 0.9, 1.0, 1.1, 2 and 3 depending on build options and the correct command line options. .IP IMAP(S) Using the mail reading protocol, curl can download emails for you. With or without using TLS. .IP LDAP(S) curl can do directory lookups for you, with or without TLS. .IP MQTT curl supports MQTT version 3. Downloading over MQTT equals subscribing to a topic while uploading/posting equals publishing on a topic. MQTT over TLS is not supported (yet). .IP POP3(S) Downloading from a pop3 server means getting an email. With or without using TLS. .IP RTSP curl supports RTSP 1.0 downloads. .IP SCP curl supports SSH version 2 scp transfers. .IP SFTP curl supports SFTP (draft 5) done over SSH version 2. .IP SMB(S) curl supports SMB version 1 for upload and download. .IP SMTP(S) Uploading contents to an SMTP server means sending an email. With or without TLS. .IP TELNET Fetching a telnet URL starts an interactive session where it sends what it reads on stdin and outputs what the server sends it. .IP TFTP curl can do TFTP downloads and uploads. .IP WS(S) WebSocket done over HTTP/1. WSS implies that it works over HTTPS. .SH PROGRESS METER curl normally displays a progress meter during operations, indicating the amount of transferred data, transfer speeds and estimated time left, etc. The progress meter displays the transfer rate in bytes per second. The used suffixes ("k" for kilo, "M" for mega, "G" for giga, "T" for tera, "P" for peta and "E" for exa) are 1024 based. For example 1k is 1024 bytes. 1M is 1048576 bytes. Strictly speaking this makes the units kibibyte and mebibyte etc. curl displays this data to the terminal by default, so if you invoke curl to do an operation and it is about to write data to the terminal, it \fIdisables\fP the progress meter as otherwise it would mess up the output mixing progress meter and response data. If you want a progress meter for HTTP POST or PUT requests, you need to redirect the response output to a file, using shell redirect (>), \fI\-\-output\fP or similar. This does not apply to FTP upload as that operation does not spit out any response data to the terminal. If you prefer a progress bar instead of the regular meter, \fI\-\-progress\-bar\fP is your friend. You can also disable the progress meter completely with the \fI\-\-silent\fP option. .SH VERSION This man page describes curl 8.21.0. If you use a later version, chances are this man page does not fully document it. If you use an earlier version, this document tries to include version information about which specific version that introduced changes. You can always learn which the latest curl version is by running .nf curl https://curl.se/info .fi The online version of this man page is always showing the latest incarnation: https://curl.se/docs/manpage.html .SH OPTIONS Options start with one or two dashes. Many of the options require an additional value next to them. If provided text does not start with a dash, it is presumed to be and treated as a URL. The short "single\-dash" form of the options, \-d for example, may be used with or without a space between it and its value, although a space is a recommended separator. The long double\-dash form, \fI\-\-data\fP for example, requires a space between it and its value. Short version options that do not need any additional values can be used immediately next to each other, like for example you can specify all the options \fI\-O\fP, \fI\-L\fP and \fI\-v\fP at once as \fI\-OLv\fP. In general, all boolean options are enabled with \--\fBoption\fP and yet again disabled with \--\fBno\-\fPoption. That is, you use the same option name but prefix it with "no\-". In this list we mostly show the \--\fBoption\fP version of them. When \fI\-\-next\fP is used, it resets the parser state and you start again with a clean option state, except for the options that are global. Global options retain their values and meaning even after \fI\-\-next\fP. If the long option name ends with an equals sign ("="), the argument is the text following on its right side. (Added in 8.16.0) The first argument that is exactly two dashes ("\--"), marks the end of options; any argument after the end of options is interpreted as a URL argument even if it starts with a dash. curl does little to no verification of the contents of command line arguments. Passing in "creative octets" like newlines might trigger unexpected results. The following options are global: \fI\-\-fail\-early\fP, \fI\-\-libcurl\fP, \fI\-\-parallel\-immediate\fP, \fI\-\-parallel\-max\-host\fP, \fI\-\-parallel\-max\fP, \fI\-\-parallel\fP, \fI\-\-progress\-bar\fP, \fI\-\-rate\fP, \fI\-\-show\-error\fP, \fI\-\-stderr\fP, \fI\-\-styled\-output\fP, \fI\-\-trace\-ascii\fP, \fI\-\-trace\-config\fP, \fI\-\-trace\-ids\fP, \fI\-\-trace\-time\fP, \fI\-\-trace\fP and \fI\-\-verbose\fP. .SH ALL OPTIONS .IP "\-\-abstract\-unix\-socket <path>" (HTTP) Connect to the server through an abstract Unix domain socket, instead of using the network. Note: netstat shows the path of an abstract socket prefixed with \&"@", however the <path> argument should not have this leading character. If \fI\-\-abstract\-unix\-socket\fP is provided several times, the last set value is used. Example: .nf curl --abstract-unix-socket socketpath https://example.com .fi See also \fI\-\-unix\-socket\fP. .IP "\-\-alt\-svc <filename>" (HTTPS) Enable the alt\-svc parser. If the filename points to an existing alt\-svc cache file, that gets used. After a completed transfer, the cache is saved to the filename again if it has been modified. Specify a "" filename (zero length) to avoid loading/saving and make curl handle the cache in memory. You may want to restrict your umask to prevent other users on the same system to access the created file. If this option is used several times, curl loads contents from all the files but the last one is used for saving. \fI\-\-alt\-svc\fP can be used several times in a command line. Example: .nf curl --alt-svc svc.txt https://example.com .fi See also \fI\-\-resolve\fP and \fI\-\-connect\-to\fP. .IP "\-\-anyauth" (HTTP) Figure out authentication method automatically, and use the most secure one the remote site claims to support. This is done by first doing a request and checking the response\-headers, thus possibly inducing an extra network round\-trip. This option is used instead of setting a specific authentication method, which you can do with \fI\-\-basic\fP, \fI\-\-digest\fP, \fI\-\-ntlm\fP, and \fI\-\-negotiate\fP. Using \fI\-\-anyauth\fP is not recommended if you do uploads from stdin, since it may require data to be sent twice and then the client must be able to rewind. If the need should arise when uploading from stdin, the upload operation fails. Used together with \fI\-\-user\fP. Example: .nf curl --anyauth --user me:pwd https://example.com .fi See also \fI\-\-proxy\-anyauth\fP, \fI\-\-basic\fP and \fI\-\-digest\fP. .IP "\-a, \-\-append" (FTP SFTP) When used in an upload, this option makes curl append to the target file instead of overwriting it. If the remote file does not exist, it is created. Note that this flag is ignored by some SFTP servers (including OpenSSH). Providing \fI\-\-append\fP multiple times has no extra effect. Disable it again with \-\-no-append. Example: .nf curl --upload-file local --append ftp://example.com/ .fi See also \fI\-\-range\fP and \fI\-\-continue\-at\fP. .IP "\-\-aws\-sigv4 <provider1[:prvdr2[:reg[:srv]]]>" (HTTP) Use AWS V4 signature authentication in the transfer. The provider argument is a string that is used by the algorithm when creating outgoing authentication headers. The region argument is a string that points to a geographic area of a resources collection (region\-code) when the region name is omitted from the endpoint. The service argument is a string that points to a function provided by a cloud (service\-code) when the service name is omitted from the endpoint. If \fI\-\-aws\-sigv4\fP is provided several times, the last set value is used. Example: .nf curl --aws-sigv4 "aws:amz:us-east-2:es" --user "key:secret" https://example.com .fi Added in 7.75.0. See also \fI\-\-basic\fP and \fI\-\-user\fP. .IP "\-\-basic" (HTTP) Use HTTP Basic authentication with the remote host. This method is the default and this option is usually pointless, unless you use it to override a previously set option that sets a different authentication method (such as \fI\-\-ntlm\fP, \fI\-\-digest\fP, or \fI\-\-negotiate\fP). Used together with \fI\-\-user\fP. Providing \fI\-\-basic\fP multiple times has no extra effect. Disable it again with \-\-no-basic. Example: .nf curl -u name:password --basic https://example.com .fi See also \fI\-\-proxy\-basic\fP. .IP "\-\-ca\-native" (TLS) Use the operating system\(aqs native CA store for certificate verification. This option is independent of other CA certificate locations set at run time or build time. Those locations are searched in addition to the native CA store. This option works with OpenSSL and its forks (BoringSSL, LibreSSL, etc) on Windows (Added in 7.71.0) and on Apple OS when libcurl is built with Apple SecTrust enabled. (Added in 8.17.0) This option works with wolfSSL on Windows, Linux (Debian, Ubuntu, Gentoo, Fedora, RHEL), macOS, Android and iOS. (Added in 8.3.0) This option works with GnuTLS (Added in 8.5.0) and also uses Apple SecTrust when libcurl is built with it. (Added in 8.17.0) This option works with Rustls on Windows, macOS, Android and iOS. On Linux it is equivalent to using the Mozilla CA certificate bundle. When used with Rustls _only_ the native CA store is consulted, not other locations set at run time or build time. (Added in 8.13.0) This option currently has no effect for Schannel. This is the native TLS library from Microsoft, that by default uses the native CA store for verification unless overridden by a CA certificate location setting. Providing \fI\-\-ca\-native\fP multiple times has no extra effect. Disable it again with \-\-no-ca-native. Example: .nf curl --ca-native https://example.com .fi Added in 8.2.0. See also \fI\-\-cacert\fP, \fI\-\-capath\fP, \fI\-\-dump\-ca\-embed\fP, \fI\-\-insecure\fP and \fI\-\-proxy\-ca\-native\fP. .IP "\-\-cacert <file>" (TLS) Use the specified certificate file to verify the peer. The file may contain multiple CA certificates. The certificate(s) must be in PEM format. Normally curl is built to use a default file for this, so this option is typically used to alter that default file. curl recognizes the environment variable named \(aqCURL_CA_BUNDLE\(aq if it is set and the TLS backend is not Schannel, and uses the given path as a path to a CA cert bundle. This option overrides that variable. (Windows) curl automatically looks for a CA certs file named \(aqcurl\-ca\-bundle.crt\(aq, either in the same directory as curl.exe, or in the Current Working Directory, or in any folder along your PATH. curl 8.11.0 added a build\-time option to disable this search behavior, and another option to restrict search to the application\(aqs directory. (Schannel) This option is supported for Schannel in Windows 7 or later (added in 7.60.0). This option is supported for backward compatibility with other SSL engines; instead it is recommended to use Windows\(aq store of root certificates (the default for Schannel). If \fI\-\-cacert\fP is provided several times, the last set value is used. Example: .nf curl --cacert CA-file.txt https://example.com .fi See also \fI\-\-capath\fP, \fI\-\-dump\-ca\-embed\fP and \fI\-\-insecure\fP. .IP "\-\-capath <dir>" (TLS) Use the specified certificate directory to verify the peer. If curl is built against OpenSSL, multiple paths can be provided by separating them with the appropriate platform\-specific separator (e.g. "path1:path2:path3" on Unix\-style platforms for "path1;path2;path3" on Windows). The certificates must be in PEM format, and if curl is built against OpenSSL, the directory must have been processed using the c_rehash utility supplied with OpenSSL. Using \fI\-\-capath\fP can allow OpenSSL\-powered curl to make SSL\-connections much more efficiently than using \fI\-\-cacert\fP if the \fI\-\-cacert\fP file contains many CA certificates. If this option is set, the default capath value is ignored. If \fI\-\-capath\fP is provided several times, the last set value is used. Example: .nf curl --capath /local/directory https://example.com .fi See also \fI\-\-cacert\fP, \fI\-\-dump\-ca\-embed\fP and \fI\-\-insecure\fP. .IP "\-E, \-\-cert <certificate[:password]>" (TLS) Use the specified client certificate file when getting a file with HTTPS, FTPS or another SSL\-based protocol. The certificate must be PEM format. If the optional password is not specified, it is queried for on the terminal. Note that this option assumes a certificate file that is the private key and the client certificate concatenated. See \fI\-\-cert\fP and \fI\-\-key\fP to specify them independently. In the <certificate> portion of the argument, you must escape the character \&":" as "\\:" so that it is not recognized as the password delimiter. Similarly, you must escape the double quote character as \\" so that it is not recognized as an escape character. If curl is built against OpenSSL, and the engine pkcs11 or pkcs11 provider is available, then a PKCS#11 URI (RFC 7512) can be used to specify a certificate located in a PKCS#11 device. A string beginning with "pkcs11:" is interpreted as a PKCS#11 URI. If a PKCS#11 URI is provided, then the \fI\-\-engine\fP option is set as "pkcs11" if none was provided and the \fI\-\-cert\-type\fP option is set as "ENG" or "PROV" if none was provided (depending on OpenSSL version). If curl is built against GnuTLS, a PKCS#11 URI can be used to specify a certificate located in a PKCS#11 device. A string beginning with "pkcs11:" is interpreted as a PKCS#11 URI. (Schannel) Client certificates must be specified by a path expression to a certificate store. (Loading \fIPFX\fP is not supported; you can import it to a store first). You can use "<store location>\\<store name>\\<thumbprint>" to refer to a certificate in the system certificates store, for example, \fI"CurrentUser\\MY\\934a7ac6f8a5d579285a74fa61e19f23ddfe8d7a"\fP. Thumbprint is usually a SHA\-1 hex string which you can see in certificate details. Following store locations are supported: \fICurrentUser\fP, \fILocalMachine\fP, \fICurrentService\fP, \fIServices\fP, \fICurrentUserGroupPolicy\fP, \fILocalMachineGroupPolicy\fP and \fILocalMachineEnterprise\fP. If \fI\-\-cert\fP is provided several times, the last set value is used. Example: .nf curl --cert certfile --key keyfile https://example.com .fi See also \fI\-\-cert\-type\fP, \fI\-\-key\fP and \fI\-\-key\-type\fP. .IP "\-\-cert\-status" (TLS) Verify the status of the server certificate by using the Certificate Status Request (aka. OCSP stapling) TLS extension. If this option is enabled and the server sends an invalid (e.g. expired) response, if the response suggests that the server certificate has been revoked, or no response at all is received, the verification fails. This support is currently only implemented in the OpenSSL and GnuTLS backends. Providing \fI\-\-cert\-status\fP multiple times has no extra effect. Disable it again with \-\-no-cert-status. Example: .nf curl --cert-status https://example.com .fi See also \fI\-\-pinnedpubkey\fP. .IP "\-\-cert\-type <type>" (TLS) Set type of the provided client certificate. PEM, DER, ENG, PROV and P12 are recognized types. The default type depends on the TLS backend and is usually PEM. For Schannel it is P12. If \fI\-\-cert\fP is a pkcs11: URI then ENG or PROV is the default type (depending on OpenSSL version). If \fI\-\-cert\-type\fP is provided several times, the last set value is used. Example: .nf curl --cert-type PEM --cert file https://example.com .fi See also \fI\-\-cert\fP, \fI\-\-key\fP and \fI\-\-key\-type\fP. .IP "\-\-ciphers <list>" (TLS) Specify which cipher suites to use in the connection if it negotiates TLS 1.2 (1.1, 1.0). The list of ciphers suites must specify valid ciphers. Read up on cipher suite details on this URL: https://curl.se/docs/ssl\-ciphers.html If \fI\-\-ciphers\fP is provided several times, the last set value is used. Example: .nf curl --ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256 https://example.com .fi See also \fI\-\-tls13\-ciphers\fP, \fI\-\-proxy\-ciphers\fP and \fI\-\-curves\fP. .IP "\-\-compressed" (HTTP) Request a compressed response using one of the algorithms curl supports, and automatically decompress the content. Response headers are not modified when saved, so if they are "interpreted" separately again at a later point they might appear to be saying that the content is (still) compressed; while in fact it has already been decompressed. If this option is used and the server sends an unsupported encoding, curl reports an error. This is a request, not an order; the server may or may not deliver data compressed. \fBWARNING\fP: when decompressing data, even tiny transfers might be expanded and generate a huge amount of bytes. You might want to limit using this option to only known and trusted sites using secure protocols, perhaps in combination with \fI\-\-max\-filesize\fP. Providing \fI\-\-compressed\fP multiple times has no extra effect. Disable it again with \-\-no-compressed. Example: .nf curl --compressed https://example.com .fi See also \fI\-\-compressed\-ssh\fP. .IP "\-\-compressed\-ssh" (SCP SFTP) Enable SSH compression. This is a request, not an order; the server may or may not do it. This allows the data to be sent compressed over the wire, and automatically decompressed in the receiving end, to save bandwidth. Providing \fI\-\-compressed\-ssh\fP multiple times has no extra effect. Disable it again with \-\-no-compressed-ssh. Example: .nf curl --compressed-ssh sftp://example.com/ .fi See also \fI\-\-compressed\fP. .IP "\-K, \-\-config <file>" Specify a text file to read curl arguments from. The command line arguments found in the text file are used as if they were provided on the command line. Options and their parameters must be specified on the same line in the file, separated by whitespace, colon, or the equals sign. Long option names can optionally be given in the config file without the initial double dashes and if so, the colon or equals characters can be used as separators. If the option is specified with one or two dashes, there can be no colon or equals character between the option and its parameter. If the parameter contains whitespace or starts with a colon (:) or equals sign (=), it must be specified enclosed within double quotes ("like this"). Within double quotes the following escape sequences are available: \\\\, \\", \\t, \\n, \\r and \\v. A backslash preceding any other letter is ignored. If the first non\-blank column of a config line is a \(aq#\(aq character, that line is treated as a comment. Only write one option per physical line in the config file. A single line is required to be no more than 10 megabytes (since 8.2.0). Specify the filename to \fI\-\-config\fP as minus "\-" to make curl read the file from stdin. Note that to be able to specify a URL in the config file, you need to specify it using the \fI\-\-url\fP option, and not by writing the URL on its own line. It could look similar to this: .nf url = "https://curl.se/docs/" # \--\- Example file \--\- # this is a comment url = "example.com" output = "curlhere.html" user\-agent = "superagent/1.0" # and fetch another URL too url = "example.com/docs/manpage.html" -O referer = "http://nowhereatall.example.com/" # \--\- End of example file \--\- .fi When curl is invoked, it (unless \fI\-\-disable\fP is used) checks for a default config file and uses it if found, even when \fI\-\-config\fP is used. The default config file is checked for in the following places in this order: 1) \fB"$CURL_HOME/.curlrc"\fP 2) \fB"$XDG_CONFIG_HOME/curlrc"\fP (Added in 7.73.0) 3) \fB"$HOME/.curlrc"\fP 4) Windows: \fB"%USERPROFILE%\\.curlrc"\fP 5) Windows: \fB"%APPDATA%\\.curlrc"\fP 6) Windows: \fB"%USERPROFILE%\\Application Data\\.curlrc"\fP 7) Non\-Windows: use getpwuid to find the home directory 8) On Windows, if it finds no \fI.curlrc\fP file in the sequence described above, it checks for one in the same directory the curl executable is placed. On Windows two filenames are checked per location: \fI.curlrc\fP and \fI_curlrc\fP, preferring the former. Older versions on Windows checked for \fI_curlrc\fP only. \fI\-\-config\fP can be used several times in a command line. Example: .nf curl --config file.txt https://example.com .fi See also \fI\-\-disable\fP. .IP "\-\-connect\-timeout <seconds>" Maximum time in seconds that you allow curl\(aqs connection to take. This only limits the connection phase, so if curl connects within the given period it continues \- if not it exits. This option accepts decimal values. The decimal value needs to be provided using a dot (.) as decimal separator \- not the local version even if it might be using another separator. The connection phase is considered complete when the DNS lookup and requested TCP, TLS or QUIC handshakes are done. If \fI\-\-connect\-timeout\fP is provided several times, the last set value is used. Examples: .nf curl --connect-timeout 20 https://example.com curl --connect-timeout 3.14 https://example.com .fi See also \fI\-\-max\-time\fP. .IP "\-\-connect\-to <HOST1:PORT1:HOST2:PORT2>" For a request intended for the "HOST1:PORT1" pair, connect to "HOST2:PORT2" instead. This option is only used to establish the network connection. It does NOT affect the hostname/port number that is used for TLS/SSL (e.g. SNI, certificate verification) or for the application protocols. \&"HOST1" and "PORT1" may be empty strings, meaning any host or any port number. \&"HOST2" and "PORT2" may also be empty strings, meaning use the request\(aqs original hostname and port number. A hostname specified to this option is compared as a string, so it needs to match the name used in the request URL. It can be either numerical such as \&"127.0.0.1" or the full hostname such as "example.org". Example: redirect connects from the example.com hostname to 127.0.0.1 independently of port number: .nf curl \--connect\-to example.com::127.0.0.1: https://example.com/ .fi Example: redirect connects from all hostnames to 127.0.0.1 independently of port number: .nf curl \--connect\-to ::127.0.0.1: http://example.com/ .fi \fI\-\-connect\-to\fP can be used several times in a command line. Example: .nf curl --connect-to example.com:443:example.net:8443 https://example.com .fi See also \fI\-\-resolve\fP and \fI\-\-header\fP. .IP "\-C, \-\-continue\-at <offset>" Resume a previous transfer from the given byte offset. The given offset is the exact number of bytes that are skipped, counting from the beginning of the source file before it is transferred to the destination. If used with uploads, the FTP server command SIZE is not used by curl. Use "\-C \-" to instruct curl to automatically find out where/how to resume the transfer. It then uses the given output/input files to figure that out. When using this option for HTTP uploads using POST or PUT, functionality is not guaranteed. The HTTP protocol has no standard interoperable resume upload and curl uses a set of headers for this purpose that once proved working for some servers and have been left for those who find that useful. This command line option is mutually exclusive with \fI\-\-range\fP: you can only use one of them for a single transfer. The \fI\-\-no\-clobber\fP and \fI\-\-remove\-on\-error\fP options cannot be used together with \fI\-\-continue\-at\fP. If \fI\-\-continue\-at\fP is provided several times, the last set value is used. Examples: .nf curl -C - https://example.com curl -C 400 https://example.com .fi See also \fI\-\-range\fP. .IP "\-b, \-\-cookie <data|filename>" (HTTP) This option has two slightly separate cookie sending functions. Either: pass the exact data to send to the HTTP server in the Cookie header. It is supposedly data previously received from the server in a "Set\-Cookie:" line. The data should be in the format "NAME1=VALUE1; NAME2=VALUE2". When given a set of specific cookies, curl populates its cookie header with this content explicitly in all outgoing request(s). If multiple requests are done due to authentication, followed redirects or similar, they all get this cookie header passed on. Or: If no "=" symbol is used in the argument, it is instead treated as a filename to read previously stored cookie from. This option also activates the cookie engine which makes curl record incoming cookies, which may be handy if you are using this in combination with the \fI\-\-location\fP option or do multiple URL transfers on the same invoke. If the filename is a single minus ("\-"), curl reads the contents from stdin. If the filename is an empty string ("") and is the only cookie input, curl activates the cookie engine without any cookies. The file format of the file to read cookies from should be plain HTTP headers (Set\-Cookie style) or the Netscape/Mozilla cookie file format. The file specified with \fI\-\-cookie\fP is only used as input. No cookies are written to that file. To store cookies, use the \fI\-\-cookie\-jar\fP option. If you use the Set\-Cookie file format and do not specify a domain then the cookie is not sent since the domain never matches. To address this, set a domain in Set\-Cookie line (doing that includes subdomains) or preferably: use the Netscape format. Users often want to both read cookies from a file and write updated cookies back to a file, so using both \fI\-\-cookie\fP and \fI\-\-cookie\-jar\fP in the same command line is common. curl ignores filenames specified with \fI\-\-cookie\fP which do not exist or point to a directory. If curl is built with PSL (\fBPublic Suffix List\fP) support, it detects and discards cookies that are specified for such suffix domains that should not be allowed to have cookies. If curl is \fInot\fP built with PSL support, it has no ability to stop super cookies. \fI\-\-cookie\fP can be used several times in a command line. Examples: .nf curl -b "" https://example.com curl -b cookiefile https://example.com curl -b cookiefile -c cookiefile https://example.com curl -b name=Jane https://example.com .fi See also \fI\-\-cookie\-jar\fP and \fI\-\-junk\-session\-cookies\fP. .IP "\-c, \-\-cookie\-jar <filename>" (HTTP) Specify to which file you want curl to write all cookies after a completed operation. curl writes all cookies from its in\-memory cookie storage to the given file at the end of operations. Even if no cookies are known, a file is created so that it removes any formerly existing cookies from the file. The file uses the Netscape cookie file format. If you set the filename to a single minus, "\-", the cookies are written to stdout. The file specified with \fI\-\-cookie\-jar\fP is only used for output. No cookies are read from the file. To read cookies, use the \fI\-\-cookie\fP option. Both options can specify the same file. This command line option activates the cookie engine that makes curl record and use cookies. The \fI\-\-cookie\fP option also activates it. If the cookie jar cannot be created or written to, the whole curl operation does not fail or even report an error clearly. Using \fI\-\-verbose\fP gets a warning displayed, but that is the only visible feedback you get about this possibly lethal situation. You may want to restrict your umask to prevent other users on the same system to access the created file. If \fI\-\-cookie\-jar\fP is provided several times, the last set value is used. Examples: .nf curl -c store-here.txt https://example.com curl -c store-here.txt -b read-these https://example.com .fi See also \fI\-\-cookie\fP and \fI\-\-junk\-session\-cookies\fP. .IP "\-\-create\-dirs" When used in conjunction with the \fI\-\-output\fP option, curl creates the necessary local directory hierarchy as needed. This option creates the directories mentioned with the \fI\-\-output\fP option combined with the path possibly set with \fI\-\-output\-dir\fP. If the combined output filename uses no directory, or if the directories it mentions already exist, no directories are created. Created directories are made with mode 0750 on Unix\-style file systems. To create remote directories when using FTP or SFTP, try \fI\-\-ftp\-create\-dirs\fP. Providing \fI\-\-create\-dirs\fP multiple times has no extra effect. Disable it again with \-\-no-create-dirs. Example: .nf curl --create-dirs --output local/dir/file https://example.com .fi See also \fI\-\-ftp\-create\-dirs\fP and \fI\-\-output\-dir\fP. .IP "\-\-create\-file\-mode <mode>" (SFTP SCP FILE) When curl is used to create files remotely using one of the supported protocols, this option allows the user to set which \(aqmode\(aq to set on the file at creation time, instead of the default 0644. This option takes an octal number as argument. If \fI\-\-create\-file\-mode\fP is provided several times, the last set value is used. Example: .nf curl --create-file-mode 0777 -T localfile sftp://example.com/new .fi Added in 7.75.0. See also \fI\-\-ftp\-create\-dirs\fP. .IP "\-\-crlf" (FTP SMTP) Convert line feeds to carriage return plus line feeds in upload. Useful for \fBMVS (OS/390)\fP. Providing \fI\-\-crlf\fP multiple times has no extra effect. Disable it again with \-\-no-crlf. Example: .nf curl --crlf -T file ftp://example.com/ .fi See also \fI\-\-use\-ascii\fP. .IP "\-\-crlfile <file>" (TLS) Provide a file using PEM format with a Certificate Revocation List that may specify peer certificates that are to be considered revoked. If \fI\-\-crlfile\fP is provided several times, the last set value is used. Example: .nf curl --crlfile rejects.txt https://example.com .fi See also \fI\-\-cacert\fP and \fI\-\-capath\fP. .IP "\-\-curves <list>" (TLS) Set specific curves to use during SSL session establishment according to RFC 8422, 5.1. Multiple algorithms can be provided by separating them with ":" (e.g. "X25519:P\-521"). The parameter is available identically in the OpenSSL \&"s_client" and "s_server" utilities. \fI\-\-curves\fP allows a OpenSSL powered curl to make SSL\-connections with exactly the (EC) curve requested by the client, avoiding nontransparent client/server negotiations. If this option is set, the default curves list built into OpenSSL are ignored. If \fI\-\-curves\fP is provided several times, the last set value is used. Example: .nf curl --curves X25519 https://example.com .fi Added in 7.73.0. See also \fI\-\-ciphers\fP. .IP "\-d, \-\-data <data>" (HTTP MQTT) Send the specified data in a POST request to the HTTP server, in the same way that a browser does when a user has filled in an HTML form and presses the submit button. This option makes curl pass the data to the server using the content\-type application/x\-www\-form\-urlencoded. Compared to \fI\-\-form\fP. \fI\-\-data\-raw\fP is almost the same but does not have a special interpretation of the @ character. To post data purely binary, you should instead use the \fI\-\-data\-binary\fP option. To URL\-encode the value of a form field you may use \fI\-\-data\-urlencode\fP. If any of these options is used more than once on the same command line, the data pieces specified are merged with a separating &\-symbol. Thus, using \(aq\-d name=daniel \-d skill=lousy\(aq would generate a post chunk that looks like \(aqname=daniel&skill=lousy\(aq. If you start the data with the letter @, the rest should be a filename to read the data from, or \- if you want curl to read the data from stdin. Posting data from a file named \(aqfoobar\(aq would thus be done with \fI\-\-data\fP @foobar. When \fI\-\-data\fP is told to read from a file like that, carriage returns, newlines and null bytes are stripped out. If you do not want the @ character to have a special interpretation use \fI\-\-data\-raw\fP instead. The data for this option is passed on to the server exactly as provided on the command line. curl does not convert, change or improve it. It is up to the user to provide the data in the correct form. \fI\-\-data\fP can be used several times in a command line. Examples: .nf curl -d "name=curl" https://example.com curl -d "name=curl" -d "tool=cmdline" https://example.com curl -d @filename https://example.com .fi This option is mutually exclusive with \fI\-\-form\fP, \fI\-\-head\fP and \fI\-\-upload\-file\fP. See also \fI\-\-data\-binary\fP, \fI\-\-data\-urlencode\fP and \fI\-\-data\-raw\fP. .IP "\-\-data\-ascii <data>" (HTTP) This option is an alias for \fI\-\-data\fP. \fI\-\-data\-ascii\fP can be used several times in a command line. Example: .nf curl --data-ascii @file https://example.com .fi See also \fI\-\-data\-binary\fP, \fI\-\-data\-raw\fP and \fI\-\-data\-urlencode\fP. .IP "\-\-data\-binary <data>" (HTTP) Post data exactly as specified with no extra processing whatsoever. If you start the data with the letter @, the rest should be a filename. \&"@\-" makes curl read the data from stdin. Data is posted in a similar manner as \fI\-\-data\fP does, except that newlines and carriage returns are preserved and conversions are never done. Like \fI\-\-data\fP the default content\-type sent to the server is application/x\-www\-form\-urlencoded. If you want the data to be treated as arbitrary binary data by the server then set the content\-type to octet\-stream: -H "Content\-Type: application/octet\-stream". If this option is used several times, the ones following the first append data as described in \fI\-\-data\fP. \fI\-\-data\-binary\fP can be used several times in a command line. Example: .nf curl --data-binary @filename https://example.com .fi See also \fI\-\-data\-ascii\fP. .IP "\-\-data\-raw <data>" (HTTP) Post data similarly to \fI\-\-data\fP but without the special interpretation of the @ character. \fI\-\-data\-raw\fP can be used several times in a command line. Examples: .nf curl --data-raw "hello" https://example.com curl --data-raw "@at@at@" https://example.com .fi See also \fI\-\-data\fP. .IP "\-\-data\-urlencode <data>" (HTTP) Post data, similar to the other \fI\-\-data\fP options with the exception that this performs URL\-encoding. To be CGI\-compliant, the <data> part should begin with a \fIname\fP followed by a separator and a content specification. The <data> part can be passed to curl using one of the following syntaxes: .RS .IP content URL\-encode the content and pass that on. Be careful so that the content does not contain any "=" or "@" symbols, as that makes the syntax match one of the other cases below. .IP =content URL\-encode the content and pass that on. The preceding "=" symbol is not included in the data. .IP name=content URL\-encode the content part and pass that on. Note that the name part is expected to be URL\-encoded already. .IP @filename load data from the given file (including any newlines), URL\-encode that data and pass it on in the POST. Using "@\-" makes curl read the data from stdin. .IP name@filename load data from the given file (including any newlines), URL\-encode that data and pass it on in the POST. The name part gets an equal sign appended, resulting in \fIname=urlencoded\-file\-content\fP. Note that the name is expected to be URL\-encoded already. .RE .IP \fI\-\-data\-urlencode\fP can be used several times in a command line. Examples: .nf curl --data-urlencode name=val https://example.com curl --data-urlencode =encodethis https://example.com curl --data-urlencode name@file https://example.com curl --data-urlencode @fileonly https://example.com .fi See also \fI\-\-data\fP and \fI\-\-data\-raw\fP. .IP "\-\-delegation <LEVEL>" (GSS/kerberos) Set LEVEL what curl is allowed to delegate when it comes to user credentials. .RS .IP none Do not allow any delegation. .IP policy Delegates if and only if the OK\-AS\-DELEGATE flag is set in the Kerberos service ticket, which is a matter of realm policy. .IP always Unconditionally allow the server to delegate. .RE .IP If \fI\-\-delegation\fP is provided several times, the last set value is used. Example: .nf curl --delegation "none" https://example.com .fi See also \fI\-\-insecure\fP and \fI\-\-ssl\fP. .IP "\-\-digest" (HTTP) Enable HTTP Digest authentication. This authentication scheme avoids sending the password over the wire in clear text. Use this in combination with the normal \fI\-\-user\fP option to set username and password. Providing \fI\-\-digest\fP multiple times has no extra effect. Disable it again with \-\-no-digest. Example: .nf curl -u name:password --digest https://example.com .fi See also \fI\-\-user\fP, \fI\-\-proxy\-digest\fP and \fI\-\-anyauth\fP. .IP "\-q, \-\-disable" If used as the \fBfirst\fP parameter on the command line, the \fIcurlrc\fP config file is not read or used. See the \fI\-\-config\fP for details on the default config file search path. Providing \fI\-\-disable\fP multiple times has no extra effect. Disable it again with \-\-no-disable. Example: .nf curl -q https://example.com .fi See also \fI\-\-config\fP. .IP "\-\-disable\-eprt" (FTP) Disable the use of the EPRT and LPRT commands when doing active FTP transfers. curl normally first attempts to use EPRT before using PORT, but with this option, it uses PORT right away. EPRT is an extension to the original FTP protocol, and does not work on all servers, but enables more functionality in a better way than the traditional PORT command. \fI\-\-eprt\fP can be used to explicitly enable EPRT again and \fI\-\-no\-eprt\fP is an alias for \fI\-\-disable\-eprt\fP. If the server is accessed using IPv6, this option has no effect as EPRT is necessary then. Disabling EPRT only changes the active behavior. If you want to switch to passive mode you need to not use \fI\-\-ftp\-port\fP or force it with \fI\-\-ftp\-pasv\fP. Providing \fI\-\-disable\-eprt\fP multiple times has no extra effect. Disable it again with \-\-no-disable-eprt. Example: .nf curl --disable-eprt ftp://example.com/ .fi See also \fI\-\-disable\-epsv\fP and \fI\-\-ftp\-port\fP. .IP "\-\-disable\-epsv" (FTP) Disable the use of the EPSV command when doing passive FTP transfers. curl normally first attempts to use EPSV before PASV, but with this option, it does not try EPSV. \fI\-\-epsv\fP can be used to explicitly enable EPSV again and \fI\-\-no\-epsv\fP is an alias for \fI\-\-disable\-epsv\fP. If the server is an IPv6 host, this option has no effect as EPSV is necessary then. Disabling EPSV only changes the passive behavior. If you want to switch to active mode you need to use \fI\-\-ftp\-port\fP. Providing \fI\-\-disable\-epsv\fP multiple times has no extra effect. Disable it again with \-\-no-disable-epsv. Example: .nf curl --disable-epsv ftp://example.com/ .fi See also \fI\-\-disable\-eprt\fP and \fI\-\-ftp\-port\fP. .IP "\-\-disallow\-username\-in\-url" Exit with error if passed a URL containing a username. Probably most useful when the URL is being provided at runtime or similar. Accepting and using credentials in a URL is normally considered a security hazard as they are easily leaked that way. Providing \fI\-\-disallow\-username\-in\-url\fP multiple times has no extra effect. Disable it again with \-\-no-disallow-username-in-url. Example: .nf curl --disallow-username-in-url https://example.com .fi See also \fI\-\-proto\fP. .IP "\-\-dns\-interface <interface>" (DNS) Send outgoing DNS requests through the given interface. This option is a counterpart to \fI\-\-interface\fP (which does not affect DNS). The supplied string must be an interface name (not an address). If \fI\-\-dns\-interface\fP is provided several times, the last set value is used. Example: .nf curl --dns-interface eth0 https://example.com .fi For \fI\-\-dns\-interface\fP to work, it requires that the underlying libcurl is built to support c-ares. See also \fI\-\-dns\-ipv4\-addr\fP and \fI\-\-dns\-ipv6\-addr\fP. .IP "\-\-dns\-ipv4\-addr <address>" (DNS) Bind to a specific IP address when making IPv4 DNS requests, so that the DNS requests originate from this address. The argument should be a single IPv4 address. If \fI\-\-dns\-ipv4\-addr\fP is provided several times, the last set value is used. Example: .nf curl --dns-ipv4-addr 10.1.2.3 https://example.com .fi For \fI\-\-dns\-ipv4\-addr\fP to work, it requires that the underlying libcurl is built to support c-ares. See also \fI\-\-dns\-interface\fP and \fI\-\-dns\-ipv6\-addr\fP. .IP "\-\-dns\-ipv6\-addr <address>" (DNS) Bind to a specific IP address when making IPv6 DNS requests, so that the DNS requests originate from this address. The argument should be a single IPv6 address. If \fI\-\-dns\-ipv6\-addr\fP is provided several times, the last set value is used. Example: .nf curl --dns-ipv6-addr 2a04:4e42::561 https://example.com .fi For \fI\-\-dns\-ipv6\-addr\fP to work, it requires that the underlying libcurl is built to support c-ares. See also \fI\-\-dns\-interface\fP and \fI\-\-dns\-ipv4\-addr\fP. .IP "\-\-dns\-servers <addresses>" (DNS) Set the list of DNS servers to be used instead of the system default. The list of IP addresses should be separated with commas. Port numbers may also optionally be given, appended to the IP address separated with a colon. If \fI\-\-dns\-servers\fP is provided several times, the last set value is used. Examples: .nf curl --dns-servers 192.168.0.1,192.168.0.2 https://example.com curl --dns-servers 10.0.0.1:53 https://example.com .fi For \fI\-\-dns\-servers\fP to work, it requires that the underlying libcurl is built to support c-ares. See also \fI\-\-dns\-interface\fP and \fI\-\-dns\-ipv4\-addr\fP. .IP "\-\-doh\-cert\-status" (DNS) Same as \fI\-\-cert\-status\fP but used for DoH (DNS\-over\-HTTPS). Verify the status of the DoH servers\(aq certificate by using the Certificate Status Request (aka. OCSP stapling) TLS extension. If this option is enabled and the DoH server sends an invalid (e.g. expired) response, if the response suggests that the server certificate has been revoked, or no response at all is received, the verification fails. This support is currently only implemented in the OpenSSL and GnuTLS backends. Providing \fI\-\-doh\-cert\-status\fP multiple times has no extra effect. Disable it again with \-\-no-doh-cert-status. Example: .nf curl --doh-cert-status --doh-url https://doh.example https://example.com .fi Added in 7.76.0. See also \fI\-\-doh\-insecure\fP. .IP "\-\-doh\-insecure" (DNS) By default, every connection curl makes to a DoH server is verified to be secure before the transfer takes place. This option tells curl to skip the verification step and proceed without checking. \fBWARNING\fP: using this option makes the DoH transfer and name resolution insecure. This option is equivalent to \fI\-\-insecure\fP and \fI\-\-proxy\-insecure\fP but used for DoH (DNS\-over\-HTTPS) only. Providing \fI\-\-doh\-insecure\fP multiple times has no extra effect. Disable it again with \-\-no-doh-insecure. Example: .nf curl --doh-insecure --doh-url https://doh.example https://example.com .fi Added in 7.76.0. See also \fI\-\-doh\-url\fP, \fI\-\-insecure\fP and \fI\-\-proxy\-insecure\fP. .IP "\-\-doh\-url <URL>" (DNS) Specify which DNS\-over\-HTTPS (DoH) server to use to resolve hostnames, instead of using the default name resolver mechanism. The URL must be HTTPS. Some SSL options that you set for your transfer also apply to DoH since the name lookups take place over SSL. The certificate verification settings are not inherited but are controlled separately via \fI\-\-doh\-insecure\fP and \fI\-\-doh\-cert\-status\fP. By default, DoH is bypassed when initially looking up DNS records of the DoH server. You can specify the IP address(es) of the DoH server with \fI\-\-resolve\fP to avoid this. This option is unset if an empty string "" is used as the URL. (Added in 7.85.0) If \fI\-\-doh\-url\fP is provided several times, the last set value is used. Examples: .nf curl --doh-url https://doh.example https://example.com curl --doh-url https://doh.example --resolve doh.example:443:192.0.2.1 https://example.com .fi See also \fI\-\-doh\-insecure\fP. .IP "\-\-dump\-ca\-embed" (TLS) Write the CA bundle embedded in curl to standard output, then quit. If curl was not built with a default CA bundle embedded, the output is empty. Providing \fI\-\-dump\-ca\-embed\fP multiple times has no extra effect. Disable it again with \-\-no-dump-ca-embed. Example: .nf curl --dump-ca-embed .fi Added in 8.10.0. See also \fI\-\-ca\-native\fP, \fI\-\-cacert\fP, \fI\-\-capath\fP, \fI\-\-proxy\-ca\-native\fP, \fI\-\-proxy\-cacert\fP and \fI\-\-proxy\-capath\fP. .IP "\-D, \-\-dump\-header <filename>" (HTTP FTP) Write the received protocol headers to the specified file. If no headers are received, the use of this option creates an empty file. Specify "\-" as filename (a single minus) to have it written to stdout. Starting in curl 8.10.0, specify "%" (a single percent sign) as filename writes the output to stderr. When used in FTP, the FTP server response lines are considered being "headers" and thus are saved there. Starting in curl 8.11.0, using the \fI\-\-create\-dirs\fP option can also create missing directory components for the path provided in \fI\-\-dump\-header\fP. Having multiple transfers in one set of operations (i.e. the URLs in one \fI\-\-next\fP clause), appends them to the same file, separated by a blank line. If \fI\-\-dump\-header\fP is provided several times, the last set value is used. Examples: .nf curl --dump-header store.txt https://example.com curl --dump-header - https://example.com -o save .fi See also \fI\-\-output\fP. .IP "\-\-ech <config>" (HTTPS) Specify how to do ECH (Encrypted Client Hello). The values allowed for <config> can be: .RS .IP false Do not attempt ECH. The is the default. .IP grease Send a GREASE ECH extension .IP true Attempt ECH if possible, but do not fail if ECH is not attempted. (The connection fails if ECH is attempted but fails.) .IP hard Attempt ECH and fail if that is not possible. ECH only works with TLS 1.3 and also requires using DoH or providing an ECHConfigList on the command line. .IP ecl:<b64val> A base64 encoded ECHConfigList that is used for ECH. .IP pn:<name> A name to use to over\-ride the "public_name" field of an ECHConfigList (only available with OpenSSL TLS support) .RE .IP Most ECH related errors cause error \fICURLE_ECH_REQUIRED\fP (101). If \fI\-\-ech\fP is provided several times, the last set value is used. Example: .nf curl --ech true https://example.com .fi Added in 8.8.0. See also \fI\-\-doh\-url\fP. .IP "\-\-egd\-file <file>" (TLS) Deprecated option (added in 7.84.0). Prior to that it only had an effect on curl if built to use old versions of OpenSSL. Specify the path name to the Entropy Gathering Daemon socket. The socket is used to seed the random engine for SSL connections. If \fI\-\-egd\-file\fP is provided several times, the last set value is used. Example: .nf curl --egd-file /random/here https://example.com .fi See also \fI\-\-random\-file\fP. .IP "\-\-engine <name>" (TLS) Select the OpenSSL crypto engine to use for cipher operations. Use "\fI\-\-engine\fP list" to print a list of build\-time supported engines. Note that not all (and possibly none) of the engines may be available at runtime. The OpenSSL concept "engines" has been superseded by "providers" in OpenSSL 3, and this option should work fine to specify such as well. If \fI\-\-engine\fP is provided several times, the last set value is used. Example: .nf curl --engine flavor https://example.com .fi See also \fI\-\-ciphers\fP and \fI\-\-curves\fP. .IP "\-\-etag\-compare <file>" (HTTP) Make a conditional HTTP request for the specific ETag read from the given file by sending a custom If\-None\-Match header using the stored ETag. For correct results, make sure that the specified file contains only a single line with the desired ETag. A non\-existing or empty file is treated as an empty ETag. Use the option \fI\-\-etag\-save\fP to first save the ETag from a response, and then use this option to compare against the saved ETag in a subsequent request. Use this option with a single URL only. If \fI\-\-etag\-compare\fP is provided several times, the last set value is used. Example: .nf curl --etag-compare etag.txt https://example.com .fi Added in 7.68.0. See also \fI\-\-etag\-save\fP and \fI\-\-time\-cond\fP. .IP "\-\-etag\-save <file>" (HTTP) Save an HTTP ETag to the specified file. An ETag is a caching related header, usually returned in a response. Use this option with a single URL only. If no ETag is sent by the server, an empty file is created. In many situations you want to use an existing etag in the request to avoid downloading the same resource again but also save the new etag if it has indeed changed, by using both etag options \fI\-\-etag\-save\fP and \fI\-\-etag\-compare\fP with the same filename, in the same command line. Starting in curl 8.12.0, using the \fI\-\-create\-dirs\fP option can also create missing directory components for the path provided in \fI\-\-etag\-save\fP. If \fI\-\-etag\-save\fP is provided several times, the last set value is used. Example: .nf curl --etag-save storetag.txt https://example.com .fi Added in 7.68.0. See also \fI\-\-etag\-compare\fP. .IP "\-\-expect100\-timeout <seconds>" (HTTP) Maximum time in seconds that you allow curl to wait for a 100\-continue response when curl emits an Expects: 100\-continue header in its request. By default curl waits one second. This option accepts decimal values. When curl stops waiting, it continues as if a response was received. The decimal value needs to be provided using a dot (".") as decimal separator \- not the local version even if it might be using another separator. If \fI\-\-expect100\-timeout\fP is provided several times, the last set value is used. Example: .nf curl --expect100-timeout 2.5 -T file https://example.com .fi See also \fI\-\-connect\-timeout\fP. .IP "\-f, \-\-fail" (HTTP) Fail with error code 22 and with no response body output at all for HTTP transfers returning HTTP response codes at 400 or greater. In normal cases when an HTTP server fails to deliver a document, it returns a body of text stating so (which often also describes why and more) and a 4xx HTTP response code. This command line option prevents curl from outputting that data and instead returns error 22 early. By default, curl does not consider HTTP response codes to indicate failure. To get both the error code and also save the content, use \fI\-\-fail\-with\-body\fP instead. This method is not fail\-safe and there are occasions where non\-successful response codes slip through, especially when authentication is involved (response codes 401 and 407). Providing \fI\-\-fail\fP multiple times has no extra effect. Disable it again with \-\-no-fail. Example: .nf curl --fail https://example.com .fi This option is mutually exclusive with \fI\-\-fail\-with\-body\fP. See also \fI\-\-fail\-with\-body\fP and \fI\-\-fail\-early\fP. .IP "\-\-fail\-early" Fail and exit on the first detected transfer error. When curl is used to do multiple transfers on the command line, it attempts to operate on each given URL, one by one. By default, it ignores errors if there are more URLs given and the last URL\(aqs success determines the error code curl returns. Early failures are "hidden" by subsequent successful transfers. Using this option, curl instead returns an error on the first transfer that fails, independent of the amount of URLs that are given on the command line. This way, no transfer failures go undetected by scripts and similar. This option does not imply \fI\-\-fail\fP, which causes transfers to fail due to the server\(aqs HTTP status code. You can combine the two options, however note \fI\-\-fail\fP is not global and is therefore contained by \fI\-\-next\fP. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-fail\-early\fP multiple times has no extra effect. Disable it again with \-\-no-fail-early. Example: .nf curl --fail-early https://example.com https://two.example .fi See also \fI\-\-fail\fP and \fI\-\-fail\-with\-body\fP. .IP "\-\-fail\-with\-body" (HTTP) Return an error on server errors where the HTTP response code is 400 or greater). In normal cases when an HTTP server fails to deliver a document, it returns an HTML document stating so (which often also describes why and more). This option allows curl to output and save that content but also to return error 22. This is an alternative option to \fI\-\-fail\fP which makes curl fail for the same circumstances but without saving the content. Providing \fI\-\-fail\-with\-body\fP multiple times has no extra effect. Disable it again with \-\-no-fail-with-body. Example: .nf curl --fail-with-body https://example.com .fi This option is mutually exclusive with \fI\-\-fail\fP. Added in 7.76.0. See also \fI\-\-fail\fP and \fI\-\-fail\-early\fP. .IP "\-\-false\-start" (TLS) No TLS backend currently supports this feature. Use false start during the TLS handshake. False start is a mode where a TLS client starts sending application data before verifying the server\(aqs Finished message, thus saving a round trip when performing a full handshake. Providing \fI\-\-false\-start\fP multiple times has no extra effect. Disable it again with \-\-no-false-start. Example: .nf curl --false-start https://example.com .fi See also \fI\-\-tcp\-fastopen\fP. .IP "\-\-follow" (HTTP) Instructs curl to follow HTTP redirects and to do the custom request method set with \fI\-\-request\fP when following redirects as the HTTP specification says. The method string set with \fI\-\-request\fP is used in subsequent requests for the status codes 307 or 308, but may be reset to GET for 301, 302 and 303. This is subtly different than \fI\-\-location\fP, as that option always sets the custom method in all subsequent requests independent of response code. Restrict which protocols a redirect is accepted to follow with \fI\-\-proto\-redir\fP. When \fI\-\-netrc\fP is used in combination with this option, credentials for the followed\-to hosts may also be selected from that file. Providing \fI\-\-follow\fP multiple times has no extra effect. Disable it again with \-\-no-follow. Example: .nf curl -X POST --follow https://example.com .fi Added in 8.16.0. See also \fI\-\-request\fP, \fI\-\-location\fP, \fI\-\-proto\-redir\fP and \fI\-\-max\-redirs\fP. .IP "\-F, \-\-form <name=content>" (HTTP SMTP IMAP) For the HTTP protocol family, emulate a filled\-in form in which a user has pressed the submit button. This makes curl POST data using the Content\-Type multipart/form\-data according to RFC 2388. For SMTP and IMAP protocols, this composes a multipart mail message to transmit. This enables uploading of binary files etc. To force the \(aqcontent\(aq part to be a file, prefix the filename with an @ sign. To get the content part from a file, prefix the filename with the symbol <. The difference between @ and < is then that @ makes a file get attached in the post as a file upload, while the < makes a text field and gets the contents for that text field from a file. Read content from stdin instead of a file by using a single "\-" as filename. This goes for both @ and < constructs. When stdin is used, the contents is buffered in memory first by curl to determine its size and allow a possible resend. Defining a part\(aqs data from a named non\-regular file (such as a named pipe or similar) is not subject to buffering and is instead read at transmission time; since the full size is unknown before the transfer starts, such data is sent as chunks by HTTP and rejected by IMAP. Example: send an image to an HTTP server, where \(aqprofile\(aq is the name of the form\-field to which the file \fBportrait.jpg\fP is the input: .nf curl \-F profile=@portrait.jpg https://example.com/upload.cgi .fi Example: send your name and shoe size in two text fields to the server: .nf curl \-F name=John \-F shoesize=11 https://example.com/ .fi Example: send your essay in a text field to the server. Send it as a plain text field, but get the contents for it from a local file: .nf curl \-F "story=<hugefile.txt" https://example.com/ .fi You can also instruct curl what Content\-Type to use by using "type=", in a manner similar to: .nf curl \-F "web=@index.html;type=text/html" example.com .fi or .nf curl \-F "name=daniel;type=text/foo" example.com .fi You can also explicitly change the name field of a file upload part by setting filename=, like this: .nf curl \-F "file=@localfile;filename=nameinpost" example.com .fi If filename/path contains \(aq,\(aq or \(aq;\(aq, it must be quoted by double\-quotes like: .nf curl \-F "file=@\\"local,file\\";filename=\\"name;in;post\\"" \\ https://example.com .fi or .nf curl \-F \(aqfile=@"local,file";filename="name;in;post"\(aq \\ https://example.com .fi Note that if a filename/path is quoted by double\-quotes, any double\-quote or backslash within the filename must be escaped by backslash. Quoting must also be applied to non\-file data if it contains semicolons, leading/trailing spaces or leading double quotes: .nf curl \-F \(aqcolors="red; green; blue";type=text/x\-myapp\(aq \\ https://example.com .fi You can add custom headers to the field by setting headers=, like .nf curl \-F "submit=OK;headers=\\"X\-submit\-type: OK\\"" example.com .fi or .nf curl \-F "submit=OK;headers=@headerfile" example.com .fi The headers= keyword may appear more than once and above notes about quoting apply. When headers are read from a file, empty lines and lines starting with \(aq#\(aq are ignored; each header can be folded by splitting between two words and starting the continuation line with a space; embedded carriage\-returns and trailing spaces are stripped. Here is an example of a header file contents: .nf # This file contains two headers. X\-header\-1: this is a header # The following header is folded. X\-header\-2: this is another header .fi To support sending multipart mail messages, the syntax is extended as follows: - name can be omitted: the equal sign is the first character of the argument, - if data starts with \(aq(\(aq, this signals to start a new multipart: it can be followed by a content type specification. - a multipart can be terminated with a \(aq=)\(aq argument. Example: the following command sends an SMTP mime email consisting in an inline part in two alternative formats: plain text and HTML. It attaches a text file: .nf curl \-F \(aq=(;type=multipart/alternative\(aq \\ \-F \(aq=plain text message\(aq \\ \-F \(aq= <body>HTML message</body>;type=text/html\(aq \\ \-F \(aq=)\(aq \-F \(aq=@textfile.txt\(aq ... smtp://example.com .fi Data can be encoded for transfer using encoder=. Available encodings are \fIbinary\fP and \fI8bit\fP that do nothing else than adding the corresponding Content\-Transfer\-Encoding header, \fI7bit\fP that only rejects 8\-bit characters with a transfer error, \fIquoted\-printable\fP and \fIbase64\fP that encodes data according to the corresponding schemes, limiting lines length to 76 characters. Example: send multipart mail with a quoted\-printable text message and a base64 attached file: .nf curl \-F \(aq=text message;encoder=quoted\-printable\(aq \\ \-F \(aq=@localfile;encoder=base64\(aq ... smtp://example.com .fi \fI\-\-form\fP can be used several times in a command line. Example: .nf curl --form "name=curl" --form "file=@loadthis" https://example.com .fi This option is mutually exclusive with \fI\-\-data\fP, \fI\-\-head\fP and \fI\-\-upload\-file\fP. See also \fI\-\-data\fP, \fI\-\-form\-string\fP and \fI\-\-form\-escape\fP. .IP "\-\-form\-escape" (HTTP IMAP SMTP) Pass on names of multipart form fields and files using backslash\-escaping instead of percent\-encoding. If \fI\-\-form\-escape\fP is provided several times, the last set value is used. Example: .nf curl --form-escape -F 'field\\name=curl' -F 'file=@load"this' https://example.com .fi Added in 7.81.0. See also \fI\-\-form\fP. .IP "\-\-form\-string <name=string>" (HTTP SMTP IMAP) Similar to \fI\-\-form\fP except that the value string for the named parameter is used literally. Leading @ and < characters, and the ";type=" string in the value have no special meaning. Use this in preference to \fI\-\-form\fP if there is any possibility that the string value may accidentally trigger the @ or < features of \fI\-\-form\fP. \fI\-\-form\-string\fP can be used several times in a command line. Example: .nf curl --form-string "name=data" https://example.com .fi See also \fI\-\-form\fP. .IP "\-\-ftp\-account <data>" (FTP) When an FTP server asks for "account data" after username and password has been provided, this data is sent off using the ACCT command. If \fI\-\-ftp\-account\fP is provided several times, the last set value is used. Example: .nf curl --ftp-account "mr.robot" ftp://example.com/ .fi See also \fI\-\-user\fP. .IP "\-\-ftp\-alternative\-to\-user <command>" (FTP) If authenticating with the USER and PASS commands fails, send this command. When connecting to Tumbleweed\(aqs Secure Transport server over FTPS using a client certificate, using "SITE AUTH" tells the server to retrieve the username from the certificate. If \fI\-\-ftp\-alternative\-to\-user\fP is provided several times, the last set value is used. Example: .nf curl --ftp-alternative-to-user "U53r" ftp://example.com .fi See also \fI\-\-ftp\-account\fP and \fI\-\-user\fP. .IP "\-\-ftp\-create\-dirs" (FTP SFTP) When an FTP or SFTP URL/operation uses a path that does not currently exist on the server, the standard behavior of curl is to fail. Using this option, curl instead attempts to create missing directories. Providing \fI\-\-ftp\-create\-dirs\fP multiple times has no extra effect. Disable it again with \-\-no-ftp-create-dirs. Example: .nf curl --ftp-create-dirs -T file ftp://example.com/remote/path/file .fi See also \fI\-\-create\-dirs\fP. .IP "\-\-ftp\-method <method>" (FTP) Control what method curl should use to reach a file on an FTP(S) server. The method argument should be one of the following alternatives: .RS .IP multicwd Do a single CWD operation for each path part in the given URL. For deep hierarchies this means many commands. This is how RFC 1738 says it should be done. This is the default but the slowest behavior. .IP nocwd Do no CWD at all. curl does SIZE, RETR, STOR etc and gives the full path to the server for each of these commands. This is the fastest behavior. .IP singlecwd Do one CWD with the full target directory and then operate on the file \&"normally" (like in the multicwd case). This is somewhat more standards compliant than "nocwd" but without the full penalty of "multicwd". .RE .IP If \fI\-\-ftp\-method\fP is provided several times, the last set value is used. Examples: .nf curl --ftp-method multicwd ftp://example.com/dir1/dir2/file curl --ftp-method nocwd ftp://example.com/dir1/dir2/file curl --ftp-method singlecwd ftp://example.com/dir1/dir2/file .fi See also \fI\-\-list\-only\fP. .IP "\-\-ftp\-pasv" (FTP) Use passive mode for the data connection. Passive is the internal default behavior, but using this option can be used to override a previous \fI\-\-ftp\-port\fP option. Reversing an enforced passive really is not doable but you must then instead enforce the correct \fI\-\-ftp\-port\fP again. Passive mode means that curl tries the EPSV command first and then PASV, unless \fI\-\-disable\-epsv\fP is used. Providing \fI\-\-ftp\-pasv\fP multiple times has no extra effect. Example: .nf curl --ftp-pasv ftp://example.com/ .fi This option is mutually exclusive with \fI\-\-ftp\-port\fP. See also \fI\-\-disable\-epsv\fP. .IP "\-P, \-\-ftp\-port <address>" (FTP) Reverse the default initiator/listener roles when connecting with FTP. This option makes curl use active mode. curl then commands the server to connect back to the client\(aqs specified address and port, while passive mode asks the server to setup an IP address and port for it to connect to. <address> should be one of: .RS .IP interface e.g. \fBeth0\fP to specify which interface\(aqs IP address you want to use (Unix only) .IP "IP address" e.g. \fB192.168.10.1\fP to specify the exact IP address .IP hostname e.g. \fBmy.host.domain\fP to specify the machine .IP - make curl pick the same IP address that is already used for the control connection. This is the recommended choice. .RE .IP Disable the use of PORT with \fI\-\-ftp\-pasv\fP. Disable the attempt to use the EPRT command instead of PORT by using \fI\-\-disable\-eprt\fP. EPRT is really PORT++. You can also append ":[start]\-[end]" to the right of the address, to tell curl what TCP port range to use. That means you specify a port range, from a lower to a higher number. A single number works as well, but do note that it increases the risk of failure since the port may not be available. If \fI\-\-ftp\-port\fP is provided several times, the last set value is used. Examples: .nf curl -P - ftp:/example.com curl -P eth0 ftp:/example.com curl -P 192.168.0.2 ftp:/example.com .fi See also \fI\-\-ftp\-pasv\fP and \fI\-\-disable\-eprt\fP. .IP "\-\-ftp\-pret" (FTP) Send a PRET command before PASV (and EPSV). Certain FTP servers, mainly drftpd, require this non\-standard command for directory listings as well as up and downloads in PASV mode. Providing \fI\-\-ftp\-pret\fP multiple times has no extra effect. Disable it again with \-\-no-ftp-pret. Example: .nf curl --ftp-pret ftp://example.com/ .fi See also \fI\-\-ftp\-port\fP and \fI\-\-ftp\-pasv\fP. .IP "\-\-ftp\-skip\-pasv\-ip" (FTP) Do not use the IP address the server suggests in its response to curl\(aqs PASV command when curl connects the data connection. Instead curl reuses the same IP address it already uses for the control connection. This option is enabled by default (added in 7.74.0). This option has no effect if PORT, EPRT or EPSV is used instead of PASV. Providing \fI\-\-ftp\-skip\-pasv\-ip\fP multiple times has no extra effect. Disable it again with \-\-no-ftp-skip-pasv-ip. Example: .nf curl --ftp-skip-pasv-ip ftp://example.com/ .fi See also \fI\-\-ftp\-pasv\fP. .IP "\-\-ftp\-ssl\-ccc" (FTP) Use CCC (Clear Command Channel) Shuts down the SSL/TLS layer after authenticating. The rest of the control channel communication is unencrypted. This allows NAT routers to follow the FTP transaction. The default mode is passive. Providing \fI\-\-ftp\-ssl\-ccc\fP multiple times has no extra effect. Disable it again with \-\-no-ftp-ssl-ccc. Example: .nf curl --ftp-ssl-ccc ftps://example.com/ .fi See also \fI\-\-ssl\fP and \fI\-\-ftp\-ssl\-ccc\-mode\fP. .IP "\-\-ftp\-ssl\-ccc\-mode <active/passive>" (FTP) Set the CCC mode. The passive mode does not initiate the shutdown, but instead waits for the server to do it, and does not reply to the shutdown from the server. The active mode initiates the shutdown and waits for a reply from the server. Providing \fI\-\-ftp\-ssl\-ccc\-mode\fP multiple times has no extra effect. Disable it again with \-\-no-ftp-ssl-ccc-mode. Example: .nf curl --ftp-ssl-ccc-mode active --ftp-ssl-ccc ftps://example.com/ .fi See also \fI\-\-ftp\-ssl\-ccc\fP. .IP "\-\-ftp\-ssl\-control" (FTP) Require SSL/TLS for the FTP login, clear for transfer. Allows secure authentication, but non\-encrypted data transfers for efficiency. Fails the transfer if the server does not support SSL/TLS. If set, this option overrides \fI\-\-ssl\fP. Providing \fI\-\-ftp\-ssl\-control\fP multiple times has no extra effect. Disable it again with \-\-no-ftp-ssl-control. Example: .nf curl --ftp-ssl-control ftp://example.com .fi See also \fI\-\-ssl\fP. .IP "\-G, \-\-get" (HTTP) When used, this option makes all data specified with \fI\-\-data\fP, \fI\-\-data\-binary\fP or \fI\-\-data\-urlencode\fP to be used in an HTTP GET request instead of the POST request that otherwise would be used. curl appends the provided data to the URL as a query string. If used in combination with \fI\-\-head\fP, the POST data is instead appended to the URL with a HEAD request. Providing \fI\-\-get\fP multiple times has no extra effect. Disable it again with \-\-no-get. Examples: .nf curl --get https://example.com curl --get -d "tool=curl" -d "age=old" https://example.com curl --get -I -d "tool=curl" https://example.com .fi See also \fI\-\-data\fP and \fI\-\-request\fP. .IP "\-g, \-\-globoff" Switch off the URL globbing function. When you set this option, you can specify URLs that contain the letters {}[] without having curl itself interpret them. Note that these letters are not normal legal URL contents but they should be encoded according to the URI standard. curl detects numerical IPv6 addresses when used in URLs and excludes them from the treatment, so they can still be used without having to disable globbing. Providing \fI\-\-globoff\fP multiple times has no extra effect. Disable it again with \-\-no-globoff. Example: .nf curl -g "https://example.com/{[]}}}}" .fi See also \fI\-\-config\fP and \fI\-\-disable\fP. .IP "\-\-happy\-eyeballs\-timeout\-ms <ms>" Set the timeout for Happy Eyeballs. Happy Eyeballs is an algorithm that attempts to connect to both IPv4 and IPv6 addresses for dual\-stack hosts, giving IPv6 a head\-start of the specified number of milliseconds. If the IPv6 address cannot be connected to within that time, then a connection attempt is made to the IPv4 address in parallel. The first connection to be established is the one that is used. The range of suggested useful values is limited. Happy Eyeballs RFC 6555 says \&"It is RECOMMENDED that connection attempts be paced 150\-250 ms apart to balance human factors against network load." libcurl currently defaults to 200 ms. Firefox and Chrome currently default to 300 ms. If \fI\-\-happy\-eyeballs\-timeout\-ms\fP is provided several times, the last set value is used. Example: .nf curl --happy-eyeballs-timeout-ms 500 https://example.com .fi See also \fI\-\-max\-time\fP and \fI\-\-connect\-timeout\fP. .IP "\-\-haproxy\-clientip <ip>" (HTTP) Set a client IP in HAProxy PROXY protocol v1 header at the beginning of the connection. For valid requests, IPv4 addresses must be indicated as a series of exactly 4 integers in the range [0..255] inclusive written in decimal representation separated by exactly one dot between each other. Heading zeroes are not permitted in front of numbers in order to avoid any possible confusion with octal numbers. IPv6 addresses must be indicated as series of 4 hexadecimal digits (upper or lower case) delimited by colons between each other, with the acceptance of one double colon sequence to replace the largest acceptable range of consecutive zeroes. The total number of decoded bits must be exactly 128. Otherwise, any string can be accepted for the client IP and get sent. It replaces \fI\-\-haproxy\-protocol\fP if used, it is not necessary to specify both flags. If \fI\-\-haproxy\-clientip\fP is provided several times, the last set value is used. Example: .nf curl --haproxy-clientip $IP .fi Added in 8.2.0. See also \fI\-\-proxy\fP. .IP "\-\-haproxy\-protocol" (HTTP) Send a HAProxy PROXY protocol v1 header at the beginning of the connection. This is used by some load balancers and reverse proxies to indicate the client\(aqs true IP address and port. This option is primarily useful when sending test requests to a service that expects this header. Providing \fI\-\-haproxy\-protocol\fP multiple times has no extra effect. Disable it again with \-\-no-haproxy-protocol. Example: .nf curl --haproxy-protocol https://example.com .fi See also \fI\-\-proxy\fP. .IP "\-I, \-\-head" (HTTP FTP FILE) Fetch the headers only. HTTP\-servers feature the command HEAD which this uses to get nothing but the header of a document. When used on an FTP or FILE URL, curl displays the file size and last modification time only. Providing \fI\-\-head\fP multiple times has no extra effect. Disable it again with \-\-no-head. Example: .nf curl -I https://example.com .fi See also \fI\-\-get\fP, \fI\-\-verbose\fP and \fI\-\-trace\-ascii\fP. .IP "\-H, \-\-header <header/@file>" (HTTP IMAP SMTP) Extra header to include in information sent. When used within an HTTP request, it is added to the regular request headers. For an IMAP or SMTP MIME uploaded mail built with \fI\-\-form\fP options, it is prepended to the resulting MIME document, effectively including it at the mail global level. It does not affect raw uploaded mails. You may specify any number of extra headers. Note that if you should add a custom header that has the same name as one of the internal ones curl would use, your externally set header is used instead of the internal one. This allows you to make even trickier stuff than curl would normally do. You should not replace internally set headers without knowing perfectly well what you are doing. Remove an internal header by giving a replacement without content on the right side of the colon, as in: \-H "Host:". If you send the custom header with no\-value then its header must be terminated with a semicolon, such as \-H \&"X\-Custom\-Header;" to send "X\-Custom\-Header:". curl makes sure that each header you add/replace is sent with the proper end\-of\-line marker, you should thus \fBnot\fP add that as a part of the header content: do not add newlines or carriage returns, they only mess things up for you. curl passes on the verbatim string you give it without any filter or other safe guards. That includes white space and control characters. This option can take an argument in @filename style, which then adds a header for each line in the input file. Using @\- makes curl read the header file from stdin. Please note that most anti\-spam utilities check the presence and value of several MIME mail headers: these are "From:", "To:", "Date:" and "Subject:" among others and should be added with this option. You need \fI\-\-proxy\-header\fP to send custom headers intended for an HTTP proxy. Passing on a "Transfer\-Encoding: chunked" header when doing an HTTP request with a request body, makes curl send the data using chunked encoding. \fBWARNING\fP: headers set with this option are set in all HTTP requests \- even after redirects are followed, like when told with \fI\-\-location\fP. This can lead to the header being sent to other hosts than the original host, so sensitive headers should be used with caution combined with following redirects. \&"Authorization:" and "Cookie:" headers are explicitly \fInot\fP passed on in HTTP requests when following redirects to other origins, unless \fI\-\-location\-trusted\fP is used. \fI\-\-header\fP can be used several times in a command line. Examples: .nf curl -H "X-First-Name: Joe" https://example.com curl -H "User-Agent: yes-please/2000" https://example.com curl -H "Host:" https://example.com curl -H @headers.txt https://example.com .fi See also \fI\-\-user\-agent\fP, \fI\-\-referer\fP and \fI\-\-proxy\-header\fP. .IP "\-h, \-\-help <subject>" Usage help. Provide help for the subject given as an optional argument. If no argument is provided, curl displays the most important command line arguments. The argument can either be a \fBcategory\fP or a \fBcommand line option\fP. When a category is provided, curl shows all command line options within the given category. Specify category "all" to list all available options. If "category" is specified, curl displays all available help categories. If the provided subject is instead an existing command line option, specified either in its short form with a single dash and a single letter, or in the long form with two dashes and a longer name, curl displays a help text for that option in the terminal. The help output is extensive for some options. If the provided command line option is not known, curl says so. Examples: .nf curl --help all curl --help --insecure curl --help -f .fi See also \fI\-\-verbose\fP. .IP "\-\-hostpubmd5 <md5>" (SFTP SCP) Pass a string containing 32 hexadecimal digits. The string should be the 128 bit \fBMD5\fP checksum of the remote host\(aqs public key, curl refuses the connection with the host unless the checksums match. If \fI\-\-hostpubmd5\fP is provided several times, the last set value is used. Example: .nf curl --hostpubmd5 e5c1c49020640a5ab0f2034854c321a8 sftp://example.com/ .fi See also \fI\-\-hostpubsha256\fP. .IP "\-\-hostpubsha256 <sha256>" (SFTP SCP) Pass a string containing a Base64\-encoded SHA256 hash of the remote host\(aqs public key. curl refuses the connection with the host unless the hashes match. If \fI\-\-hostpubsha256\fP is provided several times, the last set value is used. Example: .nf curl --hostpubsha256 NDVkMTQxMGQ1ODdmMjQ3MjczYjAyOTY5MmRkMjVmNDQ= sftp://example.com/ .fi Added in 7.80.0. See also \fI\-\-hostpubmd5\fP. .IP "\-\-hsts <filename>" (HTTPS) Enable HSTS for the transfer. If the filename points to an existing HSTS cache file, that is used. After a completed transfer, the cache is saved to the filename again if it has been modified. If you run multiple curl invokes at the same time using the same HSTS cache file, they might interfere with each other in possibly undesired ways. If curl is told to use "http://" for a transfer involving a hostname that exists in the HSTS cache, it upgrades the transfer to use HTTPS. Each HSTS cache entry has an individual lifetime after which the upgrade is no longer performed. Specify a "" filename (zero length) to avoid loading/saving and make curl handle HSTS in memory. You may want to restrict your umask to prevent other users on the same system to access the created file. If this option is used several times, curl loads contents from all the files but the last one is used for saving. Since curl 8.20.0, curl keeps no more than the most recently added 10,000 unique HSTS hostnames. \fI\-\-hsts\fP can be used several times in a command line. Example: .nf curl --hsts cache.txt https://example.com .fi Added in 7.74.0. See also \fI\-\-proto\fP. .IP "\-\-http0.9" (HTTP) Accept an HTTP version 0.9 response. HTTP/0.9 is a response without headers and therefore you can also connect with this to non\-HTTP servers and still get a response since curl transparently downgrades \- if allowed. HTTP/0.9 is disabled by default (added in 7.66.0) Providing \fI\-\-http0.9\fP multiple times has no extra effect. Disable it again with \-\-no-http0.9. Example: .nf curl --http0.9 https://example.com .fi See also \fI\-\-http1.1\fP, \fI\-\-http2\fP and \fI\-\-http3\fP. .IP "\-0, \-\-http1.0" (HTTP) Use HTTP version 1.0 instead of using its internally preferred HTTP version. Providing \fI\-\-http1.0\fP multiple times has no extra effect. Example: .nf curl --http1.0 https://example.com .fi This option is mutually exclusive with \fI\-\-http1.1\fP, \fI\-\-http2\fP, \fI\-\-http2\-prior\-knowledge\fP and \fI\-\-http3\fP. See also \fI\-\-http0.9\fP and \fI\-\-http1.1\fP. .IP "\-\-http1.1" (HTTP) Use HTTP version 1.1. This is the default with "http://" URLs. Providing \fI\-\-http1.1\fP multiple times has no extra effect. Example: .nf curl --http1.1 https://example.com .fi This option is mutually exclusive with \fI\-\-http1.0\fP, \fI\-\-http2\fP, \fI\-\-http2\-prior\-knowledge\fP and \fI\-\-http3\fP. See also \fI\-\-http1.0\fP and \fI\-\-http0.9\fP. .IP "\-\-http2" (HTTP) Use HTTP/2. For HTTPS, this means curl negotiates HTTP/2 in the TLS handshake. curl does this by default. For HTTP, this means curl attempts to upgrade the request to HTTP/2 using the Upgrade: request header. When curl uses HTTP/2 over HTTPS, it does not itself insist on TLS 1.2 or higher even though that is required by the specification. A user can add this version requirement with \fI\-\-tlsv1.2\fP. Providing \fI\-\-http2\fP multiple times has no extra effect. Example: .nf curl --http2 https://example.com .fi For \fI\-\-http2\fP to work, it requires that the underlying libcurl is built to support HTTP/2. This option is mutually exclusive with \fI\-\-http1.1\fP, \fI\-\-http1.0\fP, \fI\-\-http2\-prior\-knowledge\fP and \fI\-\-http3\fP. See also \fI\-\-http1.1\fP, \fI\-\-http3\fP, \fI\-\-no\-alpn\fP and \fI\-\-proxy\-http2\fP. .IP "\-\-http2\-prior\-knowledge" (HTTP) Issue a non\-TLS HTTP request using HTTP/2 directly without HTTP/1.1 Upgrade. It requires prior knowledge that the server supports HTTP/2 straight away. HTTPS requests still do HTTP/2 the standard way with negotiated protocol versions in the TLS handshake. Since 8.10.0 if this option is set for an HTTPS request then the application layer protocol version (ALPN) offered to the server is only HTTP/2. Prior to that both HTTP/1.1 and HTTP/2 were offered. Providing \fI\-\-http2\-prior\-knowledge\fP multiple times has no extra effect. Disable it again with \-\-no-http2-prior-knowledge. Example: .nf curl --http2-prior-knowledge https://example.com .fi For \fI\-\-http2\-prior\-knowledge\fP to work, it requires that the underlying libcurl is built to support HTTP/2. This option is mutually exclusive with \fI\-\-http1.1\fP, \fI\-\-http1.0\fP, \fI\-\-http2\fP and \fI\-\-http3\fP. See also \fI\-\-http2\fP and \fI\-\-http3\fP. .IP "\-\-http3" (HTTP) Attempt HTTP/3 to the host in the URL, but fallback to earlier HTTP versions if the HTTP/3 connection establishment fails or is slow. HTTP/3 is only available for HTTPS and not for HTTP URLs. This option allows a user to avoid using the Alt\-Svc method of upgrading to HTTP/3 when you know or suspect that the target speaks HTTP/3 on the given host and port. When asked to use HTTP/3, curl issues a separate attempt to use older HTTP versions with a slight delay, so if the HTTP/3 transfer fails or is slow, curl still tries to proceed with an older HTTP version. The fallback performs the regular negotiation between HTTP/1 and HTTP/2. Use \fI\-\-http3\-only\fP for similar functionality \fIwithout\fP a fallback. curl cannot do HTTP/3 over any proxy. Providing \fI\-\-http3\fP multiple times has no extra effect. Example: .nf curl --http3 https://example.com .fi For \fI\-\-http3\fP to work, it requires that the underlying libcurl is built to support HTTP/3. This option is mutually exclusive with \fI\-\-http1.1\fP, \fI\-\-http1.0\fP, \fI\-\-http2\fP, \fI\-\-http2\-prior\-knowledge\fP and \fI\-\-http3\-only\fP. Added in 7.66.0. See also \fI\-\-http1.1\fP and \fI\-\-http2\fP. .IP "\-\-http3\-only" (HTTP) Instruct curl to use HTTP/3 to the host in the URL, with no fallback to earlier HTTP versions. HTTP/3 can only be used for HTTPS and not for HTTP URLs. For HTTP, this option triggers an error. This option allows a user to avoid using the Alt\-Svc method of upgrading to HTTP/3 when you know that the target speaks HTTP/3 on the given host and port. This option makes curl fail if a QUIC connection cannot be established, it does not attempt any other HTTP versions on its own. Use \fI\-\-http3\fP for similar functionality \fIwith\fP a fallback. Providing \fI\-\-http3\-only\fP multiple times has no extra effect. Example: .nf curl --http3-only https://example.com .fi For \fI\-\-http3\-only\fP to work, it requires that the underlying libcurl is built to support HTTP/3. This option is mutually exclusive with \fI\-\-http1.1\fP, \fI\-\-http1.0\fP, \fI\-\-http2\fP, \fI\-\-http2\-prior\-knowledge\fP and \fI\-\-http3\fP. Added in 7.88.0. See also \fI\-\-http1.1\fP, \fI\-\-http2\fP and \fI\-\-http3\fP. .IP "\-\-ignore\-content\-length" (FTP HTTP) For HTTP, ignore the Content\-Length header. This is particularly useful for servers running Apache 1.x, which reports incorrect Content\-Length for files larger than 2 gigabytes. For FTP, this makes curl skip the SIZE command to figure out the size before downloading a file. Providing \fI\-\-ignore\-content\-length\fP multiple times has no extra effect. Disable it again with \-\-no-ignore-content-length. Example: .nf curl --ignore-content-length https://example.com .fi See also \fI\-\-ftp\-skip\-pasv\-ip\fP. .IP "\-k, \-\-insecure" (TLS SFTP SCP) By default, every secure connection curl makes is verified to be secure before the transfer takes place. This option makes curl skip the verification step and proceed without checking. When this option is not used for protocols using TLS, curl verifies the server\(aqs TLS certificate before it continues: that the certificate contains the right name which matches the hostname used in the URL and that the certificate has been signed by a CA certificate present in the cert store. See this online resource for further details: \fBhttps://curl.se/docs/sslcerts.html\fP For SFTP and SCP, this option makes curl skip the \fIknown_hosts\fP verification. \fIknown_hosts\fP is a file normally stored in the user\(aqs home directory in the \&".ssh" subdirectory, which contains hostnames and their public keys. \fBWARNING\fP: using this option makes the transfer insecure. When curl uses secure protocols it trusts responses and allows for example HSTS and Alt\-Svc information to be stored and used subsequently. Using \fI\-\-insecure\fP can make curl trust and use such information from malicious servers. Providing \fI\-\-insecure\fP multiple times has no extra effect. Disable it again with \-\-no-insecure. Example: .nf curl --insecure https://example.com .fi See also \fI\-\-proxy\-insecure\fP, \fI\-\-cacert\fP and \fI\-\-capath\fP. .IP "\-\-interface <name>" Perform the operation using a specified interface. You can enter interface name, IP address or hostname. If you prefer to be specific, you can use the following special syntax: .RS .IP if!<name> Interface name. If the provided name does not match an existing interface, curl returns with error 45. .IP host!<name> IP address or hostname. .IP ifhost!<interface>!<host> Interface name and IP address or hostname. This syntax requires libcurl 8.9.0 or later. If the provided name does not match an existing interface, curl returns with error 45. .RE .IP curl does not support using network interface names for this option on Windows. That name resolve operation if a hostname is provided does \fBnot\fP use DNS\-over\-HTTPS even if \fI\-\-doh\-url\fP is set. On Linux this option can be used to specify a \fBVRF\fP (Virtual Routing and Forwarding) device, but the binary then needs to either have the \fBCAP_NET_RAW\fP capability set or to be run as root. If \fI\-\-interface\fP is provided several times, the last set value is used. Examples: .nf curl --interface eth0 https://example.com curl --interface "host!10.0.0.1" https://example.com curl --interface "if!enp3s0" https://example.com .fi See also \fI\-\-dns\-interface\fP. .IP "\-\-ip\-tos <string>" Set Type of Service (TOS) for IPv4 or Traffic Class for IPv6. The values allowed for <string> can be a numeric value between 1 and 255 or one of the following: CS0, CS1, CS2, CS3, CS4, CS5, CS6, CS7, AF11, AF12, AF13, AF21, AF22, AF23, AF31, AF32, AF33, AF41, AF42, AF43, EF, VOICE\-ADMIT, ECT1, ECT0, CE, LE, LOWCOST, LOWDELAY, THROUGHPUT, RELIABILITY, MINCOST If \fI\-\-ip\-tos\fP is provided several times, the last set value is used. Example: .nf curl --ip-tos CS5 https://example.com .fi Added in 8.9.0. See also \fI\-\-tcp\-nodelay\fP and \fI\-\-vlan\-priority\fP. .IP "\-\-ipfs\-gateway <URL>" (IPFS) Specify which gateway to use for IPFS and IPNS URLs. Not specifying this instead makes curl check if the IPFS_GATEWAY environment variable is set, or if a "~/.ipfs/gateway" file holding the gateway URL exists. If you run a local IPFS node, this gateway is by default available under \&"http://localhost:8080". A full example URL would look like: .nf curl \--ipfs\-gateway http://localhost:8080 \\ ipfs://bafybeigagd5nmnn2iys2f3 .fi There are many public IPFS gateways. See for example: https://ipfs.github.io/public\-gateway\-checker/ If you opt to go for a remote gateway you need to be aware that you completely trust the gateway. This might be fine in local gateways that you host yourself. With remote gateways there could potentially be malicious actors returning you data that does not match the request you made, inspect or even interfere with the request. You may not notice this when using curl. A mitigation could be to go for a "trustless" gateway. This means you locally verify the data. Consult the docs page on trusted vs trustless: https://docs.ipfs.tech/reference/http/gateway/#trusted\-vs\-trustless If \fI\-\-ipfs\-gateway\fP is provided several times, the last set value is used. Example: .nf curl --ipfs-gateway https://example.com ipfs:// .fi Added in 8.4.0. See also \fI\-\-help\fP and \fI\-\-manual\fP. .IP "\-4, \-\-ipv4" Request only IPv4 addresses when resolving hostnames, and not for example any IPv6. Providing \fI\-\-ipv4\fP multiple times has no extra effect. Example: .nf curl --ipv4 https://example.com .fi This option is mutually exclusive with \fI\-\-ipv6\fP. See also \fI\-\-http1.1\fP and \fI\-\-http2\fP. .IP "\-6, \-\-ipv6" Request only IPv6 addresses when resolving hostnames, and not for example any IPv4. Your resolver may still respond to an IPv6\-only resolve request by returning IPv6 addresses that contain "mapped" IPv4 addresses for compatibility purposes. macOS is known to do this. Providing \fI\-\-ipv6\fP multiple times has no extra effect. Example: .nf curl --ipv6 https://example.com .fi This option is mutually exclusive with \fI\-\-ipv4\fP. See also \fI\-\-http1.1\fP and \fI\-\-http2\fP. .IP "\-\-json <data>" (HTTP) Send the specified JSON data in a POST request to the HTTP server. \fI\-\-json\fP works as a shortcut for passing on these three options: .nf -\-data\-binary [arg] -\-header "Content\-Type: application/json" -\-header "Accept: application/json" .fi There is \fBno verification\fP that the passed in data is actual JSON or that the syntax is correct. If you start the data with the letter @, the rest should be a filename to read the data from, or a single dash (\-) if you want curl to read the data from stdin. Posting data from a file named \(aqfoobar\(aq would thus be done with \fI\-\-json\fP @foobar and to instead read the data from stdin, use \fI\-\-json\fP @\-. If this option is used more than once on the same command line, the additional data pieces are concatenated to the previous before sending. The headers this option sets can be overridden with \fI\-\-header\fP as usual. \fI\-\-json\fP can be used several times in a command line. Examples: .nf curl --json '{ "drink": "coffee" }' https://example.com curl --json '{ "drink":' --json ' "coffee" }' https://example.com curl --json @prepared https://example.com curl --json @- https://example.com < json.txt .fi This option is mutually exclusive with \fI\-\-form\fP, \fI\-\-head\fP and \fI\-\-upload\-file\fP. Added in 7.82.0. See also \fI\-\-data\-binary\fP and \fI\-\-data\-raw\fP. .IP "\-j, \-\-junk\-session\-cookies" (HTTP) When curl is told to read cookies from a given file, this option makes it discard all session cookies. This has the same effect as if a new session is started. Typical browsers discard session cookies when they are closed down. Session cookies are cookies without a set expiry time. They are meant to only last for "a session". Providing \fI\-\-junk\-session\-cookies\fP multiple times has no extra effect. Disable it again with \-\-no-junk-session-cookies. Example: .nf curl --junk-session-cookies -b cookies.txt https://example.com .fi See also \fI\-\-cookie\fP and \fI\-\-cookie\-jar\fP. .IP "\-\-keepalive\-cnt <integer>" Set the maximum number of keepalive probes TCP should send but get no response before dropping the connection. This option is usually used in conjunction with \fI\-\-keepalive\-time\fP. This option is supported on Linux, *BSD/macOS, Windows >=10.0.16299, Solaris 11.4, and recent AIX, HP\-UX and more. This option has no effect if \fI\-\-no\-keepalive\fP is used. If unspecified, the option defaults to 9. If \fI\-\-keepalive\-cnt\fP is provided several times, the last set value is used. Example: .nf curl --keepalive-cnt 3 https://example.com .fi Added in 8.9.0. See also \fI\-\-keepalive\-time\fP and \fI\-\-no\-keepalive\fP. .IP "\-\-keepalive\-time <seconds>" Set the time a connection needs to remain idle before sending keepalive probes and the time between individual keepalive probes. It is currently effective on operating systems offering the "TCP_KEEPIDLE" and "TCP_KEEPINTVL" socket options (meaning Linux, *BSD/macOS, Windows, Solaris, and recent AIX, HP\-UX and more). Keepalive is used by the TCP stack to detect broken networks on idle connections. The number of missed keepalive probes before declaring the connection down is OS dependent and is commonly 8 (*BSD/macOS/AIX), 9 (Linux/AIX) or 5/10 (Windows), and this number can be changed by specifying the curl option "keepalive\-cnt". Note that this option has no effect if \fI\-\-no\-keepalive\fP is used. If unspecified, the option defaults to 60 seconds. If \fI\-\-keepalive\-time\fP is provided several times, the last set value is used. Example: .nf curl --keepalive-time 20 https://example.com .fi See also \fI\-\-no\-keepalive\fP, \fI\-\-keepalive\-cnt\fP and \fI\-\-max\-time\fP. .IP "\-\-key <key>" (TLS SCP SFTP) Private key filename. Allows you to provide your private key in this separate file. For SSH, if not specified, curl tries the following candidates in order: \&"~/.ssh/id_rsa", "~/.ssh/id_dsa", "./id_rsa", "./id_dsa". If curl is built against OpenSSL library, and the engine pkcs11 or pkcs11 provider is available, then a PKCS#11 URI (RFC 7512) can be used to specify a private key located in a PKCS#11 device. A string beginning with "pkcs11:" is interpreted as a PKCS#11 URI. If a PKCS#11 URI is provided, then the \fI\-\-engine\fP option is set as "pkcs11" if none was provided and the \fI\-\-key\-type\fP option is set as "ENG" or "PROV" if none was provided (depending on OpenSSL version). If curl is built against Schannel then this option is ignored for TLS protocols (HTTPS, etc). That backend expects the private key to be already present in the keychain or PKCS#12 file containing the certificate. If \fI\-\-key\fP is provided several times, the last set value is used. Example: .nf curl --cert certificate --key here https://example.com .fi See also \fI\-\-key\-type\fP and \fI\-\-cert\fP. .IP "\-\-key\-type <type>" (TLS) Private key file type. Specify which type your \fI\-\-key\fP provided private key is. DER, PEM, and ENG are supported. If not specified, PEM is assumed. If \fI\-\-key\-type\fP is provided several times, the last set value is used. Example: .nf curl --key-type DER --key here https://example.com .fi See also \fI\-\-key\fP. .IP "\-\-knownhosts <file>" (SCP SFTP) When doing SCP and SFTP transfers, curl automatically checks a database containing identification for all hosts it has ever been used with to verify that the host it connects to is the same as previously. Host keys are stored in such a known hosts file. curl uses the ~/.ssh/known_hosts in the user\(aqs home directory by default. This option lets a user specify a specific file to check the host against. The known hosts check can be disabled with \fI\-\-insecure\fP, but that makes the transfer insecure and is strongly discouraged. If \fI\-\-knownhosts\fP is provided several times, the last set value is used. Example: .nf curl --knownhosts filename --key here https://example.com .fi Added in 8.17.0. See also \fI\-\-hostpubsha256\fP, \fI\-\-hostpubmd5\fP, \fI\-\-insecure\fP and \fI\-\-key\fP. .IP "\-\-krb <level>" (FTP) Deprecated option (added in 8.17.0). It has no function anymore. Enable Kerberos authentication and use. The level must be entered and should be one of "clear", "safe", "confidential", or "private". Should you use a level that is not one of these, "private" is used. If \fI\-\-krb\fP is provided several times, the last set value is used. Example: .nf curl --krb clear ftp://example.com/ .fi For \fI\-\-krb\fP to work, it requires that the underlying libcurl is built to support Kerberos. See also \fI\-\-delegation\fP and \fI\-\-ssl\fP. .IP "\-\-libcurl <file>" Append this option to any ordinary curl command line, and you get libcurl\-using C source code written to the file that does the equivalent of what your command\-line operation does. This option is global and does not need to be specified for each use of \fI\-\-next\fP. If \fI\-\-libcurl\fP is provided several times, the last set value is used. Example: .nf curl --libcurl client.c https://example.com .fi See also \fI\-\-verbose\fP. .IP "\-\-limit\-rate <speed>" Specify the maximum transfer rate you want curl to use \- for both downloads and uploads. This feature is useful if you have a limited pipe and you would like your transfer not to use your entire bandwidth. To make it slower than it otherwise would be. The given speed is measured in bytes/second, unless a suffix is appended. Appending \(aqk\(aq or \(aqK\(aq counts the number as kilobytes, \(aqm\(aq or \(aqM\(aq makes it megabytes etc. The supported suffixes (k, M, G, T, P) are 1024\-based. For example 1k is 1024. Examples: 200K, 3m and 1G. The rate limiting logic works on averaging the transfer speed to no more than the set threshold over a period of multiple seconds. If you also use the \fI\-\-speed\-limit\fP option, that option takes precedence and might cripple the rate\-limiting slightly, to help keep the speed\-limit logic working. Starting in curl 8.19.0, the rate can be specified using a fraction as in \&"2.5M" for two and a half megabytes per second. It only works with a period (".") delimiter, independent of what your locale might prefer. If \fI\-\-limit\-rate\fP is provided several times, the last set value is used. Examples: .nf curl --limit-rate 123.45K https://example.com curl --limit-rate 1000 https://example.com curl --limit-rate 10M https://example.com curl --limit-rate 200K --max-time 60 https://example.com .fi See also \fI\-\-rate\fP, \fI\-\-speed\-limit\fP and \fI\-\-speed\-time\fP. .IP "\-l, \-\-list\-only" (FTP POP3 SFTP FILE) When listing an FTP directory, force a name\-only view. Maybe particularly useful if the user wants to machine\-parse the contents of an FTP directory since the normal directory view does not use a standard look or format. When used like this, the option causes an NLST command to be sent to the server instead of LIST. Note: Some FTP servers list only files in their response to NLST; they do not include subdirectories and symbolic links. When listing an SFTP directory, this switch forces a name\-only view, one per line. This is especially useful if the user wants to machine\-parse the contents of an SFTP directory since the normal directory view provides more information than filenames. When retrieving a specific email from POP3, this switch forces a LIST command to be performed instead of RETR. This is particularly useful if the user wants to see if a specific message\-id exists on the server and what size it is. For FILE, this option has no effect yet as directories are always listed in this mode. Note: When combined with \fI\-\-request\fP, this option can be used to send a UIDL command instead, so the user may use the email\(aqs unique identifier rather than its message\-id to make the request. Providing \fI\-\-list\-only\fP multiple times has no extra effect. Disable it again with \-\-no-list-only. Example: .nf curl --list-only ftp://example.com/dir/ .fi See also \fI\-\-quote\fP and \fI\-\-request\fP. .IP "\-\-local\-port <range>" Set a preferred single number or range (FROM\-TO) of local port numbers to use for the connection(s). Note that port numbers by nature are a scarce resource so setting this range to something too narrow might cause unnecessary connection setup failures. If \fI\-\-local\-port\fP is provided several times, the last set value is used. Example: .nf curl --local-port 1000-3000 https://example.com .fi See also \fI\-\-globoff\fP. .IP "\-L, \-\-location" (HTTP) If the server reports that the requested page has moved to a different location (indicated with a Location: header and a 3XX response code), this option makes curl redo the request to the new place. If used together with \fI\-\-show\-headers\fP or \fI\-\-head\fP, headers from all requested pages are shown. When authentication is provided on the command line (for example \fI\-\-user\fP or \fI\-\-oauth2\-bearer\fP), or when sending a cookie with "\-H Cookie:", curl only sends its credentials to the initial host. If a redirect takes curl to a different host, it does not get the credentials passed on. See \fI\-\-location\-trusted\fP on how to change this. When \fI\-\-netrc\fP is used in combination with this option, credentials for the followed\-to hosts may also be selected from that file. Limit the amount of redirects to follow by using the \fI\-\-max\-redirs\fP option. When curl follows a redirect and if the request is a POST, it sends the following request with a GET if the HTTP response was 301, 302, or 303. If the response code was any other 3xx code, curl resends the following request using the same unmodified method. You can tell curl to not change POST requests to GET after a 30x response by using the dedicated options for that: \fI\-\-post301\fP, \fI\-\-post302\fP and \fI\-\-post303\fP. The method set with \fI\-\-request\fP overrides the method curl would otherwise select to use. Restrict which protocols a redirect is accepted to follow with \fI\-\-proto\-redir\fP. Providing \fI\-\-location\fP multiple times has no extra effect. Disable it again with \-\-no-location. Example: .nf curl -L https://example.com .fi See also \fI\-\-resolve\fP, \fI\-\-alt\-svc\fP, \fI\-\-follow\fP, \fI\-\-proto\-redir\fP and \fI\-\-max\-redirs\fP. .IP "\-\-location\-trusted" (HTTP) Instruct curl to follow HTTP redirects like \fI\-\-location\fP, but permit curl to send credentials and other secrets along to other hosts than the initial one. This may or may not introduce a security breach if the site redirects you to a site to which you send this sensitive data to. Another host means that one or more of hostname, protocol scheme or port number changed. This option also allows curl to pass long cookies set explicitly with \fI\-\-header\fP. Providing \fI\-\-location\-trusted\fP multiple times has no extra effect. Disable it again with \-\-no-location-trusted. Examples: .nf curl --location-trusted -u user:password https://example.com curl --location-trusted -H "Cookie: session=abc" https://example.com .fi See also \fI\-\-user\fP and \fI\-\-follow\fP. .IP "\-\-login\-options <options>" (IMAP LDAP POP3 SMTP) Specify the login options to use during server authentication. You can use login options to specify protocol specific options that may be used during authentication. At present only IMAP, POP3 and SMTP support login options. For more information about login options please see RFC 2384, RFC 5092 and the IETF draft https://datatracker.ietf.org/doc/html/draft\-earhart\-url\-smtp\-00 Since 8.2.0, IMAP supports the login option "AUTH=+LOGIN". With this option, curl uses the plain (not SASL) "LOGIN IMAP" command even if the server advertises SASL authentication. Care should be taken in using this option, as it sends your password over the network in plain text. This does not work if the IMAP server disables the plain "LOGIN" (e.g. to prevent password snooping). If \fI\-\-login\-options\fP is provided several times, the last set value is used. Example: .nf curl --login-options 'AUTH=*' imap://example.com .fi See also \fI\-\-user\fP. .IP "\-\-mail\-auth <address>" (SMTP) Specify a single address. This is used to specify the authentication address (identity) of a submitted message that is being relayed to another server. If \fI\-\-mail\-auth\fP is provided several times, the last set value is used. Example: .nf curl --mail-auth user@example.com -T mail smtp://example.com/ .fi See also \fI\-\-mail\-rcpt\fP and \fI\-\-mail\-from\fP. .IP "\-\-mail\-from <address>" (SMTP) Specify a single address that the given mail should get sent from. If \fI\-\-mail\-from\fP is provided several times, the last set value is used. Example: .nf curl --mail-from user@example.com -T mail smtp://example.com/ .fi See also \fI\-\-mail\-rcpt\fP and \fI\-\-mail\-auth\fP. .IP "\-\-mail\-rcpt <address>" (SMTP) Specify a single email address, username or mailing list name. Repeat this option several times to send to multiple recipients. When performing an address verification (\fBVRFY\fP command), the recipient should be specified as the username or username and domain (as per Section 3.5 of RFC 5321). When performing a mailing list expand (EXPN command), the recipient should be specified using the mailing list name, such as "Friends" or "London\-Office". \fI\-\-mail\-rcpt\fP can be used several times in a command line. Example: .nf curl --mail-rcpt user@example.net smtp://example.com .fi See also \fI\-\-mail\-rcpt\-allowfails\fP. .IP "\-\-mail\-rcpt\-allowfails" (SMTP) When sending data to multiple recipients, by default curl aborts SMTP conversation if at least one of the recipients causes RCPT TO command to return an error. The default behavior can be changed by passing \fI\-\-mail\-rcpt\-allowfails\fP command\-line option which makes curl ignore errors and proceed with the remaining valid recipients. If all recipients trigger RCPT TO failures and this flag is specified, curl still aborts the SMTP conversation and returns the error received from to the last RCPT TO command. Providing \fI\-\-mail\-rcpt\-allowfails\fP multiple times has no extra effect. Disable it again with \-\-no-mail-rcpt-allowfails. Example: .nf curl --mail-rcpt-allowfails --mail-rcpt dest@example.com smtp://example.com .fi Added in 7.69.0. See also \fI\-\-mail\-rcpt\fP. .IP "\-M, \-\-manual" Manual. Display the huge help text. Example: .nf curl --manual .fi See also \fI\-\-verbose\fP, \fI\-\-libcurl\fP and \fI\-\-trace\fP. .IP "\-\-max\-filesize <bytes>" (FTP HTTP MQTT) When set to a non\-zero value, it specifies the maximum size (in bytes) of a file to download. If the file requested is larger than this value, the transfer does not start and curl returns with exit code 63. Setting the maximum value to zero disables the limit. A unit suffix letter can be used. Appending \(aqk\(aq or \(aqK\(aq counts the number as kilobytes, \(aqm\(aq or \(aqM\(aq makes it megabytes etc. The supported suffixes (k, M, G, T, P) are 1024\-based. Examples: 200K, 3m and 1G. \fBNOTE\fP: before curl 8.4.0, when the file size is not known prior to download, for such files this option has no effect even if the file transfer ends up being larger than this given limit. Starting with curl 8.4.0, this option aborts the transfer if it reaches the threshold during transfer. Starting in curl 8.19.0, the maximum size can be specified using a fraction as in "2.5M" for two and a half megabytes. It only works with a period (".") delimiter, independent of what your locale might prefer. Since 8.20.0, this option also stops ongoing transfers that would reach this threshold due to automatic decompression using \fI\-\-compressed\fP. If \fI\-\-max\-filesize\fP is provided several times, the last set value is used. Examples: .nf curl --max-filesize 100K https://example.com curl --max-filesize 2.6M https://example.com .fi See also \fI\-\-limit\-rate\fP. .IP "\-\-max\-redirs <num>" (HTTP) Set the maximum number of redirections to follow. When \fI\-\-location\fP or \fI\-\-follow\fP are used, this option prevents curl from following too many redirects. By default the limit is set to 50 redirects. Set this option to \-1 to make it unlimited. If \fI\-\-max\-redirs\fP is provided several times, the last set value is used. Example: .nf curl --max-redirs 3 --location https://example.com .fi See also \fI\-\-location\fP and \fI\-\-follow\fP. .IP "\-m, \-\-max\-time <seconds>" Set the maximum time in seconds that you allow each transfer to take. Prevents your batch jobs from hanging for hours due to slow networks or links going down. This option accepts decimal values. If you enable retrying the transfer (\fI\-\-retry\fP) then the maximum time counter is reset each time the transfer is retried. You can use \fI\-\-retry\-max\-time\fP to limit the retry time. The decimal value needs to be provided using a dot (.) as decimal separator \- not the local version even if it might be using another separator. If \fI\-\-max\-time\fP is provided several times, the last set value is used. Examples: .nf curl --max-time 10 https://example.com curl --max-time 2.92 https://example.com .fi See also \fI\-\-connect\-timeout\fP and \fI\-\-retry\-max\-time\fP. .IP "\-\-metalink" This option was previously used to specify a Metalink resource. Metalink support is disabled in curl for security reasons (added in 7.78.0). If \fI\-\-metalink\fP is provided several times, the last set value is used. Example: .nf curl --metalink file https://example.com .fi See also \fI\-\-parallel\fP. .IP "\-\-mptcp" Enable the use of Multipath TCP (MPTCP) for connections. MPTCP is an extension to the standard TCP that allows multiple TCP streams over different network paths between the same source and destination. This can enhance bandwidth and improve reliability by using multiple paths simultaneously. MPTCP is beneficial in networks where multiple paths exist between clients and servers, such as mobile networks where a device may switch between WiFi and cellular data or in wired networks with multiple Internet Service Providers. This option is currently only supported on Linux starting from kernel 5.6. Only TCP connections are modified, hence this option does not affect HTTP/3 (QUIC) or UDP connections. The server curl connects to must also support MPTCP. If not, the connection seamlessly falls back to TCP. Providing \fI\-\-mptcp\fP multiple times has no extra effect. Disable it again with \-\-no-mptcp. Example: .nf curl --mptcp https://example.com .fi Added in 8.9.0. See also \fI\-\-tcp\-fastopen\fP. .IP "\-\-negotiate" (HTTP) Enable Negotiate (SPNEGO) authentication. This option requires a library built with GSS\-API or SSPI support. Use \fI\-\-version\fP to see if your curl supports GSS\-API/SSPI or SPNEGO. When using this option, you must also provide a fake \fI\-\-user\fP option to activate the authentication code properly. Sending a \(aq\-u :\(aq is enough as the username and password from the \fI\-\-user\fP option are not actually used. Providing \fI\-\-negotiate\fP multiple times has no extra effect. Disable it again with \-\-no-negotiate. Example: .nf curl --negotiate -u : https://example.com .fi See also \fI\-\-basic\fP, \fI\-\-ntlm\fP, \fI\-\-anyauth\fP and \fI\-\-proxy\-negotiate\fP. .IP "\-n, \-\-netrc" Make curl scan the \fI.netrc\fP file in the user\(aqs home directory for login name and password. This is typically used for FTP on Unix. If used with HTTP, curl enables user authentication. See \fInetrc(5)\fP and \fIftp(1)\fP for details on the file format. curl does not complain if that file does not have the right permissions (it should be neither world\- nor group\-readable). The environment variable "HOME" is used to find the home directory. If the "NETRC" environment variable is set, that filename is used as the netrc file. (Added in 8.16.0) If \fI\-\-netrc\-file\fP is used, that overrides all other ways to figure out the file. The netrc file provides credentials for a hostname independent of which protocol and port number that are used. On Windows two filenames in the home directory are checked: \fI.netrc\fP and \fI_netrc\fP, preferring the former. Older versions on Windows checked for \fI_netrc\fP only. A quick and simple example of how to setup a \fI.netrc\fP to allow curl to access the machine host.example.com with username "myself" and password "secret" could look similar to: .nf machine host.example.com login myself password secret .fi curl also supports the "default" keyword. This is the same as machine name except that default matches any name. There can be only one "default" token, and it must be after all machine tokens. When providing a username in the URL and a \fI.netrc\fP file, curl looks for the password for that specific user for the given host if such an entry appears in the file before a "generic" "machine" entry without "login" specified. Providing \fI\-\-netrc\fP multiple times has no extra effect. Disable it again with \-\-no-netrc. Example: .nf curl --netrc https://example.com .fi This option is mutually exclusive with \fI\-\-netrc\-file\fP and \fI\-\-netrc\-optional\fP. See also \fI\-\-netrc\-file\fP, \fI\-\-config\fP and \fI\-\-user\fP. .IP "\-\-netrc\-file <filename>" Set the netrc file to use. Similar to \fI\-\-netrc\fP, except that you also provide the path (absolute or relative). It abides by \fI\-\-netrc\-optional\fP if specified. If \fI\-\-netrc\-file\fP is provided several times, the last set value is used. Example: .nf curl --netrc-file netrc https://example.com .fi This option is mutually exclusive with \fI\-\-netrc\fP. See also \fI\-\-netrc\fP, \fI\-\-user\fP and \fI\-\-config\fP. .IP "\-\-netrc\-optional" Similar to \fI\-\-netrc\fP, but this option makes the .netrc usage \fBoptional\fP and not mandatory as the \fI\-\-netrc\fP option does. Providing \fI\-\-netrc\-optional\fP multiple times has no extra effect. Disable it again with \-\-no-netrc-optional. Example: .nf curl --netrc-optional https://example.com .fi This option is mutually exclusive with \fI\-\-netrc\fP. See also \fI\-\-netrc\-file\fP. .IP "\-:, \-\-next" Use a separate operation for the following URL and associated options. This allows you to send several URL requests, each with their own specific options, for example, such as different usernames or custom requests for each. \fI\-\-next\fP resets all local options and only global ones have their values survive over to the operation following the \fI\-\-next\fP instruction. Global options include \fI\-\-verbose\fP, \fI\-\-trace\fP, \fI\-\-trace\-ascii\fP and \fI\-\-fail\-early\fP. For example, you can do both a GET and a POST in a single command line: .nf curl www1.example.com \--next \-d postthis www2.example.com .fi \fI\-\-next\fP can be used several times in a command line. Examples: .nf curl https://example.com --next -d postthis www2.example.com curl -I https://example.com --next https://example.net/ .fi See also \fI\-\-parallel\fP and \fI\-\-config\fP. .IP "\-\-no\-alpn" (HTTPS) Disable the ALPN TLS extension. ALPN is enabled by default if libcurl was built with an SSL library that supports ALPN. ALPN is used by a libcurl that supports HTTP/2 to negotiate HTTP/2 support with the server during https sessions. Note that this is the negated option name documented. You can use \fI\-\-alpn\fP to enable ALPN. Providing \fI\-\-no\-alpn\fP multiple times has no extra effect. Disable it again with \-\-alpn. Example: .nf curl --no-alpn https://example.com .fi For \fI\-\-no\-alpn\fP to work, it requires that the underlying libcurl is built to support TLS. See also \fI\-\-no\-npn\fP and \fI\-\-http2\fP. .IP "\-N, \-\-no\-buffer" Disable the buffering of the output stream. In normal work situations, curl uses a standard buffered output stream that has the effect that it outputs the data in chunks, not necessarily exactly when the data arrives. Using this option disables that buffering. Note that this is the negated option name documented. You can use \fI\-\-buffer\fP to enable buffering again. Providing \fI\-\-no\-buffer\fP multiple times has no extra effect. Disable it again with \-\-buffer. Example: .nf curl --no-buffer https://example.com .fi See also \fI\-\-progress\-bar\fP. .IP "\-\-no\-clobber" When used in conjunction with the \fI\-\-output\fP, \fI\-\-remote\-header\-name\fP, \fI\-\-remote\-name\fP, or \fI\-\-remote\-name\-all\fP options, curl avoids overwriting files that already exist. Instead, a dot and a number gets appended to the name of the file that would be created, up to filename.100 after which it does not create any file. Note that this is the negated option name documented. You can thus use \fI\-\-clobber\fP to enforce the clobbering, even if \fI\-\-remote\-header\-name\fP is specified. The \fI\-\-continue\-at\fP option cannot be used together with \fI\-\-no\-clobber\fP. Providing \fI\-\-no\-clobber\fP multiple times has no extra effect. Disable it again with \-\-clobber. Example: .nf curl --no-clobber --output local/dir/file https://example.com .fi Added in 7.83.0. See also \fI\-\-output\fP and \fI\-\-remote\-name\fP. .IP "\-\-no\-keepalive" Disable the use of keepalive messages on the TCP connection. curl otherwise enables them by default. Note that this is the negated option name documented. You can thus use \fI\-\-keepalive\fP to enforce keepalive. Providing \fI\-\-no\-keepalive\fP multiple times has no extra effect. Disable it again with \-\-keepalive. Example: .nf curl --no-keepalive https://example.com .fi See also \fI\-\-keepalive\-time\fP and \fI\-\-keepalive\-cnt\fP. .IP "\-\-no\-npn" (HTTPS) curl never uses NPN, this option has no effect (added in 7.86.0). Disable the NPN TLS extension. NPN is enabled by default if libcurl was built with an SSL library that supports NPN. NPN is used by a libcurl that supports HTTP/2 to negotiate HTTP/2 support with the server during https sessions. Providing \fI\-\-no\-npn\fP multiple times has no extra effect. Disable it again with \-\-npn. Example: .nf curl --no-npn https://example.com .fi For \fI\-\-no\-npn\fP to work, it requires that the underlying libcurl is built to support TLS. See also \fI\-\-no\-alpn\fP and \fI\-\-http2\fP. .IP "\-\-no\-progress\-meter" Option to switch off the progress meter output without muting or otherwise affecting warning and informational messages like \fI\-\-silent\fP does. Note that this is the negated option name documented. You can thus use \fI\-\-progress\-meter\fP to enable the progress meter again. Providing \fI\-\-no\-progress\-meter\fP multiple times has no extra effect. Disable it again with \-\-progress-meter. Example: .nf curl --no-progress-meter -o store https://example.com .fi Added in 7.67.0. See also \fI\-\-verbose\fP and \fI\-\-silent\fP. .IP "\-\-no\-sessionid" (TLS) Disable curl\(aqs use of SSL session\-ID caching. By default all transfers are done using the cache. Note that while nothing should ever get hurt by attempting to reuse SSL session\-IDs, there seem to be broken SSL implementations in the wild that may require you to disable this in order for you to succeed. Note that this is the negated option name documented. You can thus use \fI\-\-sessionid\fP to enforce session\-ID caching. Providing \fI\-\-no\-sessionid\fP multiple times has no extra effect. Disable it again with \-\-sessionid. Example: .nf curl --no-sessionid https://example.com .fi See also \fI\-\-insecure\fP. .IP "\-\-noproxy <no\-proxy\-list>" Comma\-separated list of hosts for which not to use a proxy, if one is specified. The only wildcard is a single "*" character, which matches all hosts, and effectively disables the proxy. Each name in this list is matched as either a domain which contains the hostname, or the hostname itself. For example, "local.com" would match "local.com", "local.com:80", and \&"www.local.com", but not "www.notlocal.com". To use international hostnames in this list, add the punycode version of the hostname. This option overrides the environment variables that disable the proxy ("no_proxy" and "NO_PROXY"). If there is an environment variable disabling a proxy, you can set the no proxy list to "" to override it. IP addresses specified to this option can be provided using CIDR notation (added in 7.86.0): an appended slash and number specifies the number of network bits out of the address to use in the comparison. For example \&"192.168.0.0/16" would match all addresses starting with "192.168". If \fI\-\-noproxy\fP is provided several times, the last set value is used. Example: .nf curl --noproxy "www.example" https://example.com .fi See also \fI\-\-proxy\fP. .IP "\-\-ntlm" (HTTP) Use NTLM authentication. The NTLM authentication method was designed by Microsoft and is used by IIS web servers. It is a proprietary protocol, reverse\-engineered by clever people and implemented in curl based on their efforts. This kind of behavior should not be endorsed, you should encourage everyone who uses NTLM to switch to a public and documented authentication method instead, such as Digest. If you want to enable NTLM for your proxy authentication, then use \fI\-\-proxy\-ntlm\fP. Providing \fI\-\-ntlm\fP multiple times has no extra effect. Disable it again with \-\-no-ntlm. Example: .nf curl --ntlm -u user:password https://example.com .fi For \fI\-\-ntlm\fP to work, it requires that the underlying libcurl is built to support TLS. See also \fI\-\-proxy\-ntlm\fP. .IP "\-\-ntlm\-wb" (HTTP) Deprecated option (added in 8.8.0). Enabled NTLM much in the style \fI\-\-ntlm\fP does, but handed over the authentication to a separate executable that was executed when needed. Providing \fI\-\-ntlm\-wb\fP multiple times has no extra effect. Example: .nf curl --ntlm-wb -u user:password https://example.com .fi See also \fI\-\-ntlm\fP and \fI\-\-proxy\-ntlm\fP. .IP "\-\-oauth2\-bearer <token>" (IMAP LDAP POP3 SMTP HTTP) Specify the Bearer Token for OAUTH 2.0 server authentication. The Bearer Token is used in conjunction with the username which can be specified as part of the \fI\-\-url\fP or \fI\-\-user\fP options. The Bearer Token and username are formatted according to RFC 6750. If \fI\-\-oauth2\-bearer\fP is provided several times, the last set value is used. Example: .nf curl --oauth2-bearer "mF_9.B5f-4.1JqM" https://example.com .fi See also \fI\-\-basic\fP, \fI\-\-ntlm\fP and \fI\-\-digest\fP. .IP "\-\-out\-null" Discard all response output of a transfer silently. This is the more efficient and portable version of .nf curl https://host.example \-o /dev/null .fi The transfer is done in full, all data is received and checked, but the bytes are not written anywhere. \fI\-\-out\-null\fP is associated with a single URL. Use it once per URL when you use several URLs in a command line. Example: .nf curl "https://example.com" --out-null .fi Added in 8.16.0. See also \fI\-\-output\fP, \fI\-\-remote\-name\fP, \fI\-\-remote\-name\-all\fP and \fI\-\-remote\-header\-name\fP. .IP "\-o, \-\-output <file>" Write output to the given file instead of stdout. If you are using globbing in the URL to fetch multiple documents, you should quote the URL and you can use \&"#" followed by a number in the filename. That variable gets replaced with the current glob text. Like in: .nf curl "http://{one,two}.example.com" \-o "file_#1.txt" .fi or use several variables like: .nf curl "http://{site,host}.host[1\-5].example" \-o "#1_#2" .fi You may use this option as many times as the number of URLs you have. For example, if you specify two URLs on the same command line, you can use it like this: .nf curl \-o aa example.com \-o bb example.net .fi and the order of the \-o options and the URLs does not matter, only that the first \-o is for the first URL and so on, so the above command line can also be written as .nf curl example.com example.net \-o aa \-o bb .fi See also the \fI\-\-create\-dirs\fP option to create the local directories dynamically. Specifying the output as \(aq\-\(aq (a single dash) passes the output to stdout. To suppress response bodies, you can redirect output to /dev/null: .nf curl example.com \-o /dev/null .fi Or for Windows: .nf curl example.com \-o nul .fi Or, even more efficient and portable, use .nf curl example.com \--out\-null .fi Specify the filename as single minus to force the output to stdout, to override curl\(aqs internal binary output in terminal prevention: .nf curl https://example.com/jpeg \-o \- .fi Note that the binary output may be caused by the response being compressed, in which case you may want to use the \fI\-\-compressed\fP option. Since curl 8.21.0, the separate globbing parts can be named and referenced by their names. The case sensitive alphanumeric name is set enclosed within angle brackets after the opening character. Examples: .nf curl "https://fun.example/{<num>one,two}.jpg" \-o "save\-#<num>" curl "ftp://ftp.example/file[<range>1\-100].txt" \\ \-o "save\-#<range>.txt" .fi Referencing a named glob that is not set, causes an error. Since curl 8.21.0, you can use parts of the upload filename when it uses globbing by setting a glob name and referencing it the same way you reference named URL globs. For example, if you upload three files to a single fixed HTTP URL and want to save the corresponding responses in separate files: .nf curl \-T \(aqfile{<num>1,2,3}\(aq \\ https://upload.example/ \-o \(aqresponse\-#<num>\(aq .fi \fI\-\-output\fP is associated with a single URL. Use it once per URL when you use several URLs in a command line. Examples: .nf curl -o file https://example.com curl "http://{one,two}.example.com" -o "file_#1.txt" curl "http://{site,host}.host[1-5].example" -o "#1_#2" curl -o file https://example.com -o file2 https://example.net .fi See also \fI\-\-out\-null\fP, \fI\-\-remote\-name\fP, \fI\-\-remote\-name\-all\fP, \fI\-\-remote\-header\-name\fP and \fI\-\-compressed\fP. .IP "\-\-output\-dir <dir>" Specify the directory in which files should be stored, when \fI\-\-remote\-name\fP or \fI\-\-output\fP are used. The given output directory is used for all URLs and output options on the command line, up until the first \fI\-\-next\fP. If the specified target directory does not exist, the operation fails unless \fI\-\-create\-dirs\fP is also used. If \fI\-\-output\-dir\fP is provided several times, the last set value is used. Example: .nf curl --output-dir "tmp" -O https://example.com .fi Added in 7.73.0. See also \fI\-\-remote\-name\fP and \fI\-\-remote\-header\-name\fP. .IP "\-Z, \-\-parallel" Make curl perform all transfers in parallel as compared to the regular serial manner. Parallel transfer means that curl runs up to N concurrent transfers simultaneously and if there are more than N transfers to handle, it starts new ones when earlier transfers finish. With parallel transfers, the progress meter output is different from when doing serial transfers, as it then displays the transfer status for multiple transfers in a single line. The maximum amount of concurrent transfers is set with \fI\-\-parallel\-max\fP and it defaults to 50. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-parallel\fP multiple times has no extra effect. Disable it again with \-\-no-parallel. Example: .nf curl --parallel https://example.com -o file1 https://example.com -o file2 .fi Added in 7.66.0. See also \fI\-\-next\fP, \fI\-\-verbose\fP, \fI\-\-parallel\-max\fP and \fI\-\-parallel\-immediate\fP. .IP "\-\-parallel\-immediate" When doing parallel transfers, this option instructs curl to prefer opening up more connections in parallel at once rather than waiting to see if new transfers can be added as multiplexed streams on another connection. By default, without this option set, curl prefers to wait a little and multiplex new transfers over existing connections. It keeps the number of connections low at the expense of risking a slightly slower transfer startup. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-parallel\-immediate\fP multiple times has no extra effect. Disable it again with \-\-no-parallel-immediate. Example: .nf curl --parallel-immediate -Z https://example.com -o file1 https://example.com -o file2 .fi Added in 7.68.0. See also \fI\-\-parallel\fP and \fI\-\-parallel\-max\fP. .IP "\-\-parallel\-max <num>" When asked to do parallel transfers, using \fI\-\-parallel\fP, this option controls the maximum amount of transfers to do simultaneously. The default is 50. 65535 is the largest supported value. This option is global and does not need to be specified for each use of \fI\-\-next\fP. If \fI\-\-parallel\-max\fP is provided several times, the last set value is used. Example: .nf curl --parallel-max 100 -Z https://example.com ftp://example.com/ .fi Added in 7.66.0. See also \fI\-\-parallel\fP and \fI\-\-parallel\-max\-host\fP. .IP "\-\-parallel\-max\-host <num>" When asked to do parallel transfers, using \fI\-\-parallel\fP, this option controls the maximum amount of concurrent connections curl is allowed to do to the same protocol + hostname + port number target. The limit is enforced by libcurl and queued "internally", which means that transfers that are waiting for an available connection still look like started transfers in the progress meter. The default is 0 (unlimited). 65535 is the largest supported value. This option is global and does not need to be specified for each use of \fI\-\-next\fP. If \fI\-\-parallel\-max\-host\fP is provided several times, the last set value is used. Example: .nf curl --parallel-max-host 5 -Z https://example.com ftp://example.com/ .fi Added in 8.16.0. See also \fI\-\-parallel\fP and \fI\-\-parallel\-max\fP. .IP "\-\-pass <phrase>" (TLS SCP SFTP) Passphrase for the private key used for SSH or TLS. If \fI\-\-pass\fP is provided several times, the last set value is used. Example: .nf curl --pass secret --key file https://example.com .fi See also \fI\-\-key\fP and \fI\-\-user\fP. .IP "\-\-path\-as\-is" Do not handle sequences of /../ or /./ in the given URL path. Normally curl squashes or merges them according to standards but with this option set you tell it not to do that. Providing \fI\-\-path\-as\-is\fP multiple times has no extra effect. Disable it again with \-\-no-path-as-is. Example: .nf curl --path-as-is https://example.com/../../etc/passwd .fi See also \fI\-\-request\-target\fP. .IP "\-\-pinnedpubkey <hashes>" (TLS) Use the specified public key file (or hashes) to verify the peer. This can be a path to a file which contains a single public key in PEM or DER format, or any number of base64 encoded sha256 hashes preceded by \(aqsha256//\(aq and separated by \(aq;\(aq. When negotiating a TLS or SSL connection, the server sends a certificate indicating its identity. A public key is extracted from this certificate and if it does not exactly match the public key provided to this option, curl aborts the connection before sending or receiving any data. This option is independent of option \fI\-\-insecure\fP. If you use both options together then the peer is still verified by public key. PEM/DER support: OpenSSL and GnuTLS, wolfSSL, mbedTLS, Schannel sha256 support: OpenSSL, GnuTLS and wolfSSL, mbedTLS, Schannel Other SSL backends not supported. If \fI\-\-pinnedpubkey\fP is provided several times, the last set value is used. Examples: .nf curl --pinnedpubkey keyfile https://example.com curl --pinnedpubkey 'sha256//ce118b51897f4452dc' https://example.com .fi See also \fI\-\-hostpubsha256\fP. .IP "\-\-post301" (HTTP) Respect RFC 7231/6.4.2 and do not convert POST requests into GET requests when following a 301 redirect. The non\-RFC behavior is ubiquitous in web browsers, so curl does the conversion by default to maintain consistency. A server may require a POST to remain a POST after such a redirection. This option is meaningful only when using \fI\-\-location\fP. Providing \fI\-\-post301\fP multiple times has no extra effect. Disable it again with \-\-no-post301. Example: .nf curl --post301 --location -d "data" https://example.com .fi See also \fI\-\-post302\fP, \fI\-\-post303\fP and \fI\-\-location\fP. .IP "\-\-post302" (HTTP) Respect RFC 7231/6.4.3 and do not convert POST requests into GET requests when following a 302 redirect. The non\-RFC behavior is ubiquitous in web browsers, so curl does the conversion by default to maintain consistency. A server may require a POST to remain a POST after such a redirection. This option is meaningful only when using \fI\-\-location\fP. Providing \fI\-\-post302\fP multiple times has no extra effect. Disable it again with \-\-no-post302. Example: .nf curl --post302 --location -d "data" https://example.com .fi See also \fI\-\-post301\fP, \fI\-\-post303\fP and \fI\-\-location\fP. .IP "\-\-post303" (HTTP) Violate RFC 7231/6.4.4 and do not convert POST requests into GET requests when following 303 redirect. A server may require a POST to remain a POST after a 303 redirection. This option is meaningful only when using \fI\-\-location\fP. Providing \fI\-\-post303\fP multiple times has no extra effect. Disable it again with \-\-no-post303. Example: .nf curl --post303 --location -d "data" https://example.com .fi See also \fI\-\-post302\fP, \fI\-\-post301\fP and \fI\-\-location\fP. .IP "\-\-preproxy <[protocol://]host[:port]>" Use the specified SOCKS proxy before connecting to an HTTP or HTTPS \fI\-\-proxy\fP. In such a case curl first connects to the SOCKS proxy and then connects (through SOCKS) to the HTTP or HTTPS proxy. Hence pre proxy. The pre proxy string should be specified with a "protocol://" prefix to specify alternative proxy protocols. Use "socks4://", "socks4a://", "socks5://" or \&"socks5h://" to request the specific SOCKS version to be used. No protocol specified makes curl default to SOCKS4. If the port number is not specified in the proxy string, it is assumed to be 1080. User and password that might be provided in the proxy string are URL decoded by curl. This allows you to pass in special characters such as @ by using %40 or pass in a colon with %3a. If \fI\-\-preproxy\fP is provided several times, the last set value is used. Example: .nf curl --preproxy socks5://proxy.example -x http://http.example https://example.com .fi See also \fI\-\-proxy\fP and \fI\-\-socks5\fP. .IP "\-#, \-\-progress\-bar" Make curl display transfer progress as a simple progress bar instead of the standard, more informational, meter. This progress bar draws a single line of \(aq#\(aq characters across the screen and shows a percentage if the transfer size is known. For transfers without a known size, there is a space ship (\-=o=\-) that moves back and forth but only while data is being transferred, with a set of flying hash sign symbols on top. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-progress\-bar\fP multiple times has no extra effect. Disable it again with \-\-no-progress-bar. Example: .nf curl -# -O https://example.com .fi See also \fI\-\-styled\-output\fP. .IP "\-\-proto <protocols>" Limit what protocols to allow for transfers. Protocols are evaluated left to right, are comma separated, and are each a protocol name or \(aqall\(aq, optionally prefixed by zero or more modifiers. Available modifiers are: .RS .IP + Permit this protocol in addition to protocols already permitted (this is the default if no modifier is used). .IP - Deny this protocol, removing it from the list of protocols already permitted. .IP = Permit only this protocol (ignoring the list already permitted), though subject to later modification by subsequent entries in the comma separated list. .RE .IP For example: \fI\-\-proto\fP \-ftps uses the default protocols, but disables ftps \fI\-\-proto\fP \-all,https,+http only enables http and https \fI\-\-proto\fP =http,https also only enables http and https Unknown and disabled protocols produce a warning. This allows scripts to safely rely on being able to disable potentially dangerous protocols, without relying upon support for that protocol being built into curl to avoid an error. This option can be used multiple times, in which case the effect is the same as concatenating the protocols into one instance of the option. If \fI\-\-proto\fP is provided several times, the last set value is used. Example: .nf curl --proto =http,https,sftp https://example.com .fi See also \fI\-\-proto\-redir\fP and \fI\-\-proto\-default\fP. .IP "\-\-proto\-default <protocol>" Use \fIprotocol\fP for any provided URL missing a scheme. The case\-insensitive name should be given without any "://" suffix. An unknown or unsupported protocol causes error \fICURLE_UNSUPPORTED_PROTOCOL\fP. This option does not change the default proxy protocol (http). Without this option set, curl guesses protocol based on the hostname, see \fI\-\-url\fP for details. The default protocol cannot be set to "ipfs" or "ipns". Those schemes need to be used explicitly in the URL. If \fI\-\-proto\-default\fP is provided several times, the last set value is used. Example: .nf curl --proto-default https ftp.example.com .fi See also \fI\-\-proto\fP and \fI\-\-proto\-redir\fP. .IP "\-\-proto\-redir <protocols>" Limit what protocols to allow on redirects. Protocols denied by \fI\-\-proto\fP are not overridden by this option. See \fI\-\-proto\fP for how protocols are represented. Example, allow only HTTP and HTTPS on redirect: .nf curl \--proto\-redir \-all,http,https \--follow http://example.com .fi By default curl only allows HTTP, HTTPS, FTP and FTPS on redirects \&. Specifying \fIall\fP or \fI+all\fP enables all protocols on redirects, which is not good for security. If \fI\-\-proto\-redir\fP is provided several times, the last set value is used. Example: .nf curl --proto-redir =http,https --follow https://example.com .fi See also \fI\-\-proto\fP and \fI\-\-follow\fP. .IP "\-x, \-\-proxy <[protocol://]host[:port]>" Use the specified proxy. The proxy string can be specified with a "protocol://" prefix. No protocol specified or http:// it is treated as an HTTP proxy. Use "socks4://", \&"socks4a://", "socks5://" or "socks5h://" to request a specific SOCKS version to be used. Unix domain sockets are supported for socks proxy. Set localhost for the host part. e.g. socks5h://localhost/path/to/socket.sock HTTPS proxy support works with the "https://" protocol prefix for OpenSSL and GnuTLS. It also works for mbedTLS, Rustls, Schannel and wolfSSL (added in 7.87.0). Unrecognized and unsupported proxy protocol schemes cause an error. If the port number is not specified in the proxy string, it is assumed to be 1080. This option overrides existing environment variables that set the proxy to use. If there is an environment variable setting a proxy, you can set proxy to \&"" to override it. All operations that are performed over an HTTP proxy are transparently converted to HTTP. It means that certain protocol specific operations might not be available. This is not the case if you can tunnel through the proxy, as one with the \fI\-\-proxytunnel\fP option. User and password that might be provided in the proxy string are URL decoded by curl. This allows you to pass in special characters such as @ by using %40 or pass in a colon with %3a. The proxy host can be specified the same way as the proxy environment variables, including the protocol prefix ("http://") and the embedded user + password. When a proxy is used, the active FTP mode as set with \fI\-\-ftp\-port\fP, cannot be used. Doing FTP over an HTTP proxy without \fI\-\-proxytunnel\fP makes curl do HTTP with an FTP URL over the proxy. For such transfers, common FTP specific options do not work, including \fI\-\-ssl\-reqd\fP and \fI\-\-ftp\-ssl\-control\fP. If \fI\-\-proxy\fP is provided several times, the last set value is used. Example: .nf curl --proxy http://proxy.example https://example.com .fi See also \fI\-\-socks5\fP and \fI\-\-proxy\-basic\fP. .IP "\-\-proxy\-anyauth" Automatically pick a suitable authentication method when communicating with the given HTTP proxy. This might cause an extra request/response round\-trip. Example: .nf curl --proxy-anyauth --proxy-user user:passwd -x proxy https://example.com .fi See also \fI\-\-proxy\fP, \fI\-\-proxy\-basic\fP and \fI\-\-proxy\-digest\fP. .IP "\-\-proxy\-basic" Use HTTP Basic authentication when communicating with the given proxy. Use \fI\-\-basic\fP for enabling HTTP Basic with a remote host. Basic is the default authentication method curl uses with proxies. Providing \fI\-\-proxy\-basic\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-basic. Example: .nf curl --proxy-basic --proxy-user user:passwd -x proxy https://example.com .fi See also \fI\-\-proxy\fP, \fI\-\-proxy\-anyauth\fP and \fI\-\-proxy\-digest\fP. .IP "\-\-proxy\-ca\-native" (TLS) Use the operating system\(aqs native CA store for certificate verification of the HTTPS proxy. This option is independent of other HTTPS proxy CA certificate locations set at run time or build time. Those locations are searched in addition to the native CA store. Equivalent to \fI\-\-ca\-native\fP but used in HTTPS proxy context. Refer to \fI\-\-ca\-native\fP for TLS backend limitations. Providing \fI\-\-proxy\-ca\-native\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-ca-native. Example: .nf curl --proxy-ca-native https://example.com .fi Added in 8.2.0. See also \fI\-\-ca\-native\fP, \fI\-\-cacert\fP, \fI\-\-capath\fP, \fI\-\-dump\-ca\-embed\fP and \fI\-\-insecure\fP. .IP "\-\-proxy\-cacert <file>" Use the specified certificate file to verify the HTTPS proxy. The file may contain multiple CA certificates. The certificate(s) must be in PEM format. This allows you to use a different trust for the proxy compared to the remote server connected to via the proxy. Equivalent to \fI\-\-cacert\fP but used in HTTPS proxy context. If \fI\-\-proxy\-cacert\fP is provided several times, the last set value is used. Example: .nf curl --proxy-cacert CA-file.txt -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\-capath\fP, \fI\-\-cacert\fP, \fI\-\-capath\fP, \fI\-\-dump\-ca\-embed\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-capath <dir>" Same as \fI\-\-capath\fP but used in HTTPS proxy context. Use the specified certificate directory to verify the proxy. Multiple paths can be provided by separating them with colon (":") (e.g. "path1:path2:path3"). The certificates must be in PEM format, and if curl is built against OpenSSL, the directory must have been processed using the c_rehash utility supplied with OpenSSL. Using \fI\-\-proxy\-capath\fP can allow OpenSSL\-powered curl to make SSL\-connections much more efficiently than using \fI\-\-proxy\-cacert\fP if the \fI\-\-proxy\-cacert\fP file contains many CA certificates. If this option is set, the default capath value is ignored. If \fI\-\-proxy\-capath\fP is provided several times, the last set value is used. Example: .nf curl --proxy-capath /local/directory -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\-cacert\fP, \fI\-\-proxy\fP, \fI\-\-capath\fP and \fI\-\-dump\-ca\-embed\fP. .IP "\-\-proxy\-cert <cert[:passwd]>" Use the specified client certificate file when communicating with an HTTPS proxy. The certificate must be PEM format. If the optional password is not specified, it is queried for on the terminal. Use \fI\-\-proxy\-key\fP to provide the private key. This option is the equivalent to \fI\-\-cert\fP but used in HTTPS proxy context. If \fI\-\-proxy\-cert\fP is provided several times, the last set value is used. Example: .nf curl --proxy-cert file -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\fP, \fI\-\-proxy\-key\fP and \fI\-\-proxy\-cert\-type\fP. .IP "\-\-proxy\-cert\-type <type>" Set type of the provided client certificate when using HTTPS proxy. PEM, DER, ENG, PROV and P12 are recognized types. The default type depends on the TLS backend and is usually PEM. For Schannel it is P12. If \fI\-\-proxy\-cert\fP is a pkcs11: URI then ENG or PROV is the default type (depending on OpenSSL version). Equivalent to \fI\-\-cert\-type\fP but used in HTTPS proxy context. If \fI\-\-proxy\-cert\-type\fP is provided several times, the last set value is used. Example: .nf curl --proxy-cert-type PEM --proxy-cert file -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\-cert\fP and \fI\-\-proxy\-key\fP. .IP "\-\-proxy\-ciphers <list>" (TLS) Same as \fI\-\-ciphers\fP but used in HTTPS proxy context. Specify which cipher suites to use in the connection to your HTTPS proxy when it negotiates TLS 1.2 (1.1, 1.0). The list of ciphers suites must specify valid ciphers. Read up on cipher suite details on this URL: https://curl.se/docs/ssl\-ciphers.html If \fI\-\-proxy\-ciphers\fP is provided several times, the last set value is used. Example: .nf curl --proxy-ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256 -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\-tls13\-ciphers\fP, \fI\-\-ciphers\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-crlfile <file>" Provide filename for a PEM formatted file with a Certificate Revocation List that specifies peer certificates that are considered revoked when communicating with an HTTPS proxy. Equivalent to \fI\-\-crlfile\fP but only used in HTTPS proxy context. If \fI\-\-proxy\-crlfile\fP is provided several times, the last set value is used. Example: .nf curl --proxy-crlfile rejects.txt -x https://proxy.example https://example.com .fi See also \fI\-\-crlfile\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-digest" Use HTTP Digest authentication when communicating with the given proxy. Use \fI\-\-digest\fP for enabling HTTP Digest with a remote host. Providing \fI\-\-proxy\-digest\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-digest. Example: .nf curl --proxy-digest --proxy-user user:passwd -x proxy https://example.com .fi See also \fI\-\-proxy\fP, \fI\-\-proxy\-anyauth\fP and \fI\-\-proxy\-basic\fP. .IP "\-\-proxy\-header <header/@file>" (HTTP) Extra header to include in the request when sending HTTP to a proxy. You may specify any number of extra headers. This is the equivalent option to \fI\-\-header\fP but is for proxy communication only like in CONNECT requests when you want a separate header sent to the proxy to what is sent to the actual remote host. curl makes sure that each header you add/replace is sent with the proper end\-of\-line marker, you should thus \fBnot\fP add that as a part of the header content: do not add newlines or carriage returns, they only mess things up for you. Headers specified with this option are not included in requests that curl knows are not to be sent to a proxy. This option can take an argument in @filename style, which then adds a header for each line in the input file. Using @\- makes curl read the headers from stdin. This option can be used multiple times to add/replace/remove multiple headers. \fI\-\-proxy\-header\fP can be used several times in a command line. Examples: .nf curl --proxy-header "X-First-Name: Joe" -x http://proxy https://example.com curl --proxy-header "User-Agent: surprise" -x http://proxy https://example.com curl --proxy-header "Host:" -x http://proxy https://example.com .fi See also \fI\-\-proxy\fP and \fI\-\-header\fP. .IP "\-\-proxy\-http2" (HTTP) Negotiate HTTP/2 with an HTTPS proxy. The proxy might still only offer HTTP/1 and then curl sticks to using that version. This has no effect for any other kinds of proxies. This option is mutually exclusive with "\fI\-\-proxy\-http3\fP". Providing \fI\-\-proxy\-http2\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-http2. Example: .nf curl --proxy-http2 -x proxy https://example.com .fi For \fI\-\-proxy\-http2\fP to work, it requires that the underlying libcurl is built to support HTTP/2. This option is mutually exclusive with \fI\-\-proxy\-http3\fP. Added in 8.1.0. See also \fI\-\-proxy\fP. .IP "\-\-proxy\-http3" (HTTP) Negotiate HTTP/3 with an HTTPS proxy. Fails to perform the transfer if the given proxy does not support HTTP/3. This has no effect for any other kinds of proxies. This option is mutually exclusive with "\fI\-\-proxy\-http2\fP". This feature is experimental and requires a build with HTTP/3 proxy support enabled. For autotools builds, use "\fI\-\-enable\-proxy\-http3\fP". For CMake builds, use "\-DUSE_PROXY_HTTP3=ON". Providing \fI\-\-proxy\-http3\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-http3. Example: .nf curl --proxy-http3 -x proxy https://example.com .fi For \fI\-\-proxy\-http3\fP to work, it requires that the underlying libcurl is built to support HTTP/3. This option is mutually exclusive with \fI\-\-proxy\-http2\fP. Added in 8.21.0. See also \fI\-\-proxy\fP and \fI\-\-proxy\-http2\fP. .IP "\-\-proxy\-insecure" Same as \fI\-\-insecure\fP but used in HTTPS proxy context. Every secure connection curl makes is verified to be secure before the transfer takes place. This option makes curl skip the verification step with a proxy and proceed without checking. When this option is not used for a proxy using HTTPS, curl verifies the proxy\(aqs TLS certificate before it continues: that the certificate contains the right name which matches the hostname and that the certificate has been signed by a CA certificate present in the cert store. See this online resource for further details: \fBhttps://curl.se/docs/sslcerts.html\fP \fBWARNING\fP: using this option makes the transfer to the proxy insecure. Providing \fI\-\-proxy\-insecure\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-insecure. Example: .nf curl --proxy-insecure -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\fP and \fI\-\-insecure\fP. .IP "\-\-proxy\-key <key>" Specify the filename for your private key when using client certificates with your HTTPS proxy. This option is the equivalent to \fI\-\-key\fP but used in HTTPS proxy context. If \fI\-\-proxy\-key\fP is provided several times, the last set value is used. Example: .nf curl --proxy-key here -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\-key\-type\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-key\-type <type>" Specify the private key file type your \fI\-\-proxy\-key\fP provided private key uses. DER, PEM, and ENG are supported. If not specified, PEM is assumed. Equivalent to \fI\-\-key\-type\fP but used in HTTPS proxy context. If \fI\-\-proxy\-key\-type\fP is provided several times, the last set value is used. Example: .nf curl --proxy-key-type DER --proxy-key here -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\-key\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-negotiate" Use HTTP Negotiate (SPNEGO) authentication when communicating with the given proxy. Use \fI\-\-negotiate\fP for enabling HTTP Negotiate (SPNEGO) with a remote host. Providing \fI\-\-proxy\-negotiate\fP multiple times has no extra effect. Example: .nf curl --proxy-negotiate --proxy-user user:passwd -x proxy https://example.com .fi See also \fI\-\-proxy\-anyauth\fP, \fI\-\-proxy\-basic\fP and \fI\-\-proxy\-service\-name\fP. .IP "\-\-proxy\-ntlm" Use HTTP NTLM authentication when communicating with the given proxy. Use \fI\-\-ntlm\fP for enabling NTLM with a remote host. Providing \fI\-\-proxy\-ntlm\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-ntlm. Example: .nf curl --proxy-ntlm --proxy-user user:passwd -x http://proxy https://example.com .fi See also \fI\-\-proxy\-negotiate\fP, \fI\-\-proxy\-anyauth\fP and \fI\-\-proxy\-user\fP. .IP "\-\-proxy\-pass <phrase>" Passphrase for the private key for HTTPS proxy client certificate. Equivalent to \fI\-\-pass\fP but used in HTTPS proxy context. If \fI\-\-proxy\-pass\fP is provided several times, the last set value is used. Example: .nf curl --proxy-pass secret --proxy-key here -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\fP and \fI\-\-proxy\-key\fP. .IP "\-\-proxy\-pinnedpubkey <hashes>" (TLS) Use the specified public key file (or hashes) to verify the proxy. This can be a path to a file which contains a single public key in PEM or DER format, or any number of base64 encoded sha256 hashes preceded by \(aqsha256//\(aq and separated by \(aq;\(aq. When negotiating a TLS or SSL connection, the server sends a certificate indicating its identity. A public key is extracted from this certificate and if it does not exactly match the public key provided to this option, curl aborts the connection before sending or receiving any data. Before curl 8.10.0 this option did not work due to a bug. If \fI\-\-proxy\-pinnedpubkey\fP is provided several times, the last set value is used. Examples: .nf curl --proxy-pinnedpubkey keyfile https://example.com curl --proxy-pinnedpubkey 'sha256//ce118b51897f4452dc' https://example.com .fi See also \fI\-\-pinnedpubkey\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-service\-name <name>" Set the service name for SPNEGO when doing proxy authentication. If \fI\-\-proxy\-service\-name\fP is provided several times, the last set value is used. Example: .nf curl --proxy-service-name "shrubbery" -x proxy https://example.com .fi See also \fI\-\-service\-name\fP, \fI\-\-proxy\fP and \fI\-\-proxy\-negotiate\fP. .IP "\-\-proxy\-ssl\-allow\-beast" Do not work around a security flaw in the TLS1.0 protocol known as BEAST when communicating to an HTTPS proxy. If this option is not used, the TLS layer may use workarounds known to cause interoperability problems with some older server implementations. This option only changes how curl does TLS 1.0 with an HTTPS proxy and has no effect on later TLS versions. \fBWARNING\fP: this option loosens the TLS security, and by using this flag you ask for exactly that. Equivalent to \fI\-\-ssl\-allow\-beast\fP but used in HTTPS proxy context. Providing \fI\-\-proxy\-ssl\-allow\-beast\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-ssl-allow-beast. Example: .nf curl --proxy-ssl-allow-beast -x https://proxy.example https://example.com .fi See also \fI\-\-ssl\-allow\-beast\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-ssl\-auto\-client\-cert" Same as \fI\-\-ssl\-auto\-client\-cert\fP but used in HTTPS proxy context. This is only supported by Schannel. Providing \fI\-\-proxy\-ssl\-auto\-client\-cert\fP multiple times has no extra effect. Disable it again with \-\-no-proxy-ssl-auto-client-cert. Example: .nf curl --proxy-ssl-auto-client-cert -x https://proxy.example https://example.com .fi Added in 7.77.0. See also \fI\-\-ssl\-auto\-client\-cert\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-tls13\-ciphers <list>" (TLS) Same as \fI\-\-tls13\-ciphers\fP but used in HTTPS proxy context. Specify which cipher suites to use in the connection to your HTTPS proxy when it negotiates TLS 1.3. The list of ciphers suites must specify valid ciphers. Read up on TLS 1.3 cipher suite details on this URL: https://curl.se/docs/ssl\-ciphers.html This option is used when curl is built to use OpenSSL 1.1.1 or later, Schannel, wolfSSL, or mbedTLS 3.6.0 or later. Before curl 8.10.0 with mbedTLS or wolfSSL, TLS 1.3 cipher suites were set by using the \fI\-\-proxy\-ciphers\fP option. If \fI\-\-proxy\-tls13\-ciphers\fP is provided several times, the last set value is used. Example: .nf curl --proxy-tls13-ciphers TLS_AES_128_GCM_SHA256 -x proxy https://example.com .fi See also \fI\-\-proxy\-ciphers\fP, \fI\-\-tls13\-ciphers\fP and \fI\-\-proxy\fP. .IP "\-\-proxy\-tlsauthtype <type>" Set TLS authentication type with HTTPS proxy. The only supported option is \&"SRP", for TLS\-SRP (RFC 5054). This option works only if the underlying libcurl is built with TLS\-SRP support. Equivalent to \fI\-\-tlsauthtype\fP but used in HTTPS proxy context. If \fI\-\-proxy\-tlsauthtype\fP is provided several times, the last set value is used. Example: .nf curl --proxy-tlsauthtype SRP -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\fP, \fI\-\-proxy\-tlsuser\fP and \fI\-\-proxy\-tlspassword\fP. .IP "\-\-proxy\-tlspassword <string>" Set password to use with the TLS authentication method specified with \fI\-\-proxy\-tlsauthtype\fP when using HTTPS proxy. Requires that \fI\-\-proxy\-tlsuser\fP is set. This option does not work with TLS 1.3. Equivalent to \fI\-\-tlspassword\fP but used in HTTPS proxy context. If \fI\-\-proxy\-tlspassword\fP is provided several times, the last set value is used. Example: .nf curl --proxy-tlspassword passwd -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\fP and \fI\-\-proxy\-tlsuser\fP. .IP "\-\-proxy\-tlsuser <name>" Set username for use for HTTPS proxy with the TLS authentication method specified with \fI\-\-proxy\-tlsauthtype\fP. Requires that \fI\-\-proxy\-tlspassword\fP also is set. This option does not work with TLS 1.3. If \fI\-\-proxy\-tlsuser\fP is provided several times, the last set value is used. Example: .nf curl --proxy-tlsuser smith -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\fP and \fI\-\-proxy\-tlspassword\fP. .IP "\-\-proxy\-tlsv1" Use at least TLS version 1.x when negotiating with an HTTPS proxy. That means TLS version 1.0 or higher Equivalent to \fI\-\-tlsv1\fP but for an HTTPS proxy context. Providing \fI\-\-proxy\-tlsv1\fP multiple times has no extra effect. Example: .nf curl --proxy-tlsv1 -x https://proxy.example https://example.com .fi See also \fI\-\-proxy\fP. .IP "\-U, \-\-proxy\-user <user:password>" Specify the username and password to use for proxy authentication. If you use a Windows SSPI\-enabled curl binary and do either Negotiate or NTLM authentication then you can tell curl to select the username and password from your environment by specifying a single colon with this option: "\-U :". On systems where it works, curl hides the given option argument from process listings. This is not enough to protect credentials from possibly getting seen by other users on the same system as they still are visible for a moment before being cleared. Such sensitive data should be retrieved from a file instead or similar and never used in clear text in a command line. If \fI\-\-proxy\-user\fP is provided several times, the last set value is used. Example: .nf curl --proxy-user smith:secret -x proxy https://example.com .fi See also \fI\-\-proxy\-pass\fP. .IP "\-\-proxy1.0 <host[:port]>" Use the specified HTTP 1.0 proxy. If the port number is not specified, it is assumed at port 1080. The only difference between this and the HTTP proxy option \fI\-\-proxy\fP, is that attempts to use CONNECT through the proxy specifies an HTTP 1.0 protocol instead of the default HTTP 1.1. Providing \fI\-\-proxy1.0\fP multiple times has no extra effect. Example: .nf curl --proxy1.0 http://proxy https://example.com .fi See also \fI\-\-proxy\fP, \fI\-\-socks5\fP and \fI\-\-preproxy\fP. .IP "\-p, \-\-proxytunnel" When an HTTP proxy is used \fI\-\-proxy\fP, this option makes curl tunnel the traffic through the proxy. The tunnel approach is made with the HTTP proxy CONNECT request and requires that the proxy allows direct connection to the remote port number curl wants to tunnel through to. To suppress proxy CONNECT response headers when curl is set to output headers use \fI\-\-suppress\-connect\-headers\fP. Providing \fI\-\-proxytunnel\fP multiple times has no extra effect. Disable it again with \-\-no-proxytunnel. Example: .nf curl --proxytunnel -x http://proxy https://example.com .fi See also \fI\-\-proxy\fP. .IP "\-\-pubkey <key>" (SFTP SCP) Public key filename. Allows you to provide your public key in this separate file. curl attempts to automatically extract the public key from the private key file, so passing this option is generally not required. Note that this public key extraction requires libcurl to be linked against a copy of libssh2 1.2.8 or higher that is itself linked against OpenSSL. If \fI\-\-pubkey\fP is provided several times, the last set value is used. Example: .nf curl --pubkey file.pub sftp://example.com/ .fi See also \fI\-\-pass\fP. .IP "\-Q, \-\-quote <command>" (FTP SFTP) Send an arbitrary command to the remote FTP or SFTP server. Quote commands are sent BEFORE the transfer takes place (immediately after the initial \fBPWD\fP command in an FTP transfer, to be exact). To make commands take place after a successful transfer, prefix them with a dash \(aq\-\(aq. (FTP only) To make commands be sent after curl has changed the working directory, immediately before the file transfer command(s), prefix the command with a \(aq+\(aq. You may specify any number of commands. By default curl stops at first failure. To make curl continue even if the command fails, prefix the command with an asterisk (*). Otherwise, if the server returns failure for one of the commands, the entire operation is aborted. You must send syntactically correct FTP commands as RFC 959 defines to FTP servers, or one of the commands listed below to SFTP servers. SFTP is a binary protocol. Unlike for FTP, curl interprets SFTP quote commands itself before sending them to the server. Filenames must be provided within double quotes to embed spaces, backslashes, quotes or double quotes. Within double quotes the following escape sequences are available for that purpose: \\\\, \\", and \\\(aq. Following is the list of all supported SFTP quote commands: .RS .IP "atime date file" The atime command sets the last access time of the file named by the file operand. The date expression can be all sorts of date strings, see the \fIcurl_getdate(3)\fP man page for date expression details. (Added in 7.73.0) .IP "chgrp group file" The chgrp command sets the group ID of the file named by the file operand to the group ID specified by the group operand. The group operand is a decimal integer group ID. .IP "chmod mode file" The chmod command modifies the file mode bits of the specified file. The mode operand is an octal integer mode number. .IP "chown user file" The chown command sets the owner of the file named by the file operand to the user ID specified by the user operand. The user operand is a decimal integer user ID. .IP "ln source_file target_file" The ln and symlink commands create a symbolic link at the target_file location pointing to the source_file location. .IP "mkdir directory_name" The mkdir command creates the directory named by the directory_name operand. .IP "mtime date file" The mtime command sets the last modification time of the file named by the file operand. The date expression can be all sorts of date strings, see the \fIcurl_getdate(3)\fP man page for date expression details. (Added in 7.73.0) .IP pwd The pwd command returns the absolute path name of the current working directory. .IP "rename source target" The rename command renames the file or directory named by the source operand to the destination path named by the target operand. .IP "rm file" The rm command removes the file specified by the file operand. .IP "rmdir directory" The rmdir command removes the directory entry specified by the directory operand, provided it is empty. .IP "symlink source_file target_file" See ln. .RE .IP \fI\-\-quote\fP can be used several times in a command line. Example: .nf curl --quote "DELE file" ftp://example.com/foo .fi See also \fI\-\-request\fP. .IP "\-\-random\-file <file>" Deprecated option. This option is ignored (added in 7.84.0). Prior to that it only had an effect on curl if built to use old versions of OpenSSL. Specify the path name to file containing random data. The data may be used to seed the random engine for SSL connections. If \fI\-\-random\-file\fP is provided several times, the last set value is used. Example: .nf curl --random-file rubbish https://example.com .fi See also \fI\-\-egd\-file\fP. .IP "\-r, \-\-range <range>" (HTTP FTP SFTP FILE) Retrieve a byte range (i.e. a partial document) from an HTTP/1.1, FTP or SFTP server or a local FILE. Ranges can be specified in a number of ways. .RS .IP 0-499 specifies the first 500 bytes .IP 500-999 specifies the second 500 bytes .IP -500 specifies the last 500 bytes .IP 9500- specifies the bytes from offset 9500 and forward .IP 0-0,-1 specifies the first and last byte only(*)(HTTP) .IP 100-199,500-599 specifies two separate 100\-byte ranges(*) (HTTP) .RE .IP (*) = NOTE that if specifying multiple ranges and the server supports it then it replies with a multiple part response that curl returns as\-is. It contains meta information in addition to the requested bytes. Parsing or otherwise transforming this response is the responsibility of the caller. Only digit characters (0\-9) are valid in the \(aqstart\(aq and \(aqstop\(aq fields of the \(aqstart\-stop\(aq range syntax. If a non\-digit character is given in the range, the server\(aqs response is unspecified, depending on the server\(aqs configuration. Many HTTP/1.1 servers do not have this feature enabled, so that when you attempt to get a range, curl instead gets the whole document. FTP and SFTP range downloads only support the simple \(aqstart\-stop\(aq syntax (optionally with one of the numbers omitted). FTP use depends on the extended FTP command SIZE. When using this option for HTTP uploads using POST or PUT, functionality is not guaranteed. The HTTP protocol has no standard interoperable resume upload and curl uses a set of headers for this purpose that once proved working for some servers and have been left for those who find that useful. This command line option is mutually exclusive with \fI\-\-continue\-at\fP: you can only use one of them for a single transfer. If \fI\-\-range\fP is provided several times, the last set value is used. Example: .nf curl --range 22-44 https://example.com .fi See also \fI\-\-continue\-at\fP and \fI\-\-append\fP. .IP "\-\-rate <max request rate>" Specify the maximum transfer frequency you allow curl to use \- in number of transfer starts per time unit (sometimes called request rate). Without this option, curl starts the next transfer as fast as possible. If given several URLs and a transfer completes faster than the allowed rate, curl waits until the next transfer is started to maintain the requested rate. This option has no effect when \fI\-\-parallel\fP is used. The request rate is provided as "N/U" where N is an integer number and U is a time unit. Supported units are \(aqs\(aq (second), \(aqm\(aq (minute), \(aqh\(aq (hour) and \(aqd\(aq /(day, as in a 24 hour unit). The default time unit, if no "/U" is provided, is number of transfers per hour. If curl is told to allow 10 requests per minute, it does not start the next request until 6 seconds have elapsed since the previous transfer was started. This function uses millisecond resolution. If the allowed frequency is set more than 1000 per second, it instead runs unrestricted. When retrying transfers, enabled with \fI\-\-retry\fP, the separate retry delay logic is used and not this setting. Starting in version 8.10.0, you can specify the number of time units in the rate expression. Make curl do no more than 5 transfers per 15 seconds with "5/15s" or limit it to 3 transfers per 4 hours with "3/4h". No spaces allowed. This option is global and does not need to be specified for each use of \fI\-\-next\fP. If \fI\-\-rate\fP is provided several times, the last set value is used. Examples: .nf curl --rate 2/s https://example.com ... curl --rate 3/h https://example.com ... curl --rate 14/m https://example.com ... .fi Added in 7.84.0. See also \fI\-\-limit\-rate\fP and \fI\-\-retry\-delay\fP. .IP "\-\-raw" (HTTP) When used, it disables all internal HTTP decoding of content or transfer encodings and instead makes them passed on unaltered, raw. Providing \fI\-\-raw\fP multiple times has no extra effect. Disable it again with \-\-no-raw. Example: .nf curl --raw https://example.com .fi See also \fI\-\-tr\-encoding\fP. .IP "\-e, \-\-referer <URL>" (HTTP) Set the referrer URL in the HTTP request. This can also be set with the \fI\-\-header\fP flag of course. When used with \fI\-\-location\fP you can append ";auto"" to the \fI\-\-referer\fP URL to make curl automatically set the previous URL when it follows a Location: header. The ";auto" string can be used alone, even if you do not set an initial \fI\-\-referer\fP. If \fI\-\-referer\fP is provided several times, the last set value is used. Examples: .nf curl --referer "https://fake.example" https://example.com curl --referer "https://fake.example;auto" -L https://example.com curl --referer ";auto" -L https://example.com .fi See also \fI\-\-user\-agent\fP and \fI\-\-header\fP. .IP "\-J, \-\-remote\-header\-name" (HTTP) Tell the \fI\-\-remote\-name\fP option to use the server\-specified Content\-Disposition filename instead of extracting a filename from the URL. If the server\-provided filename contains a path, that is stripped off before the filename is used. The file is saved in the current directory, or in the directory specified with \fI\-\-output\-dir\fP. If the server specifies a filename and a file with that name already exists in the destination directory, it is not overwritten and an error occurs \- unless you allow it by using the \fI\-\-clobber\fP option. If the server does not specify a filename then this option has no effect. There is no attempt to decode %\-sequences (yet) in the provided filename, so this option may provide you with rather unexpected filenames. This feature uses the name from the "filename" field, it does not yet support the "filename*" field (filenames with explicit character sets). Starting in 8.19.0, curl falls back and uses the filename extracted from the last redirect header if no "Content\-Disposition:" header provides a filename. \fBWARNING\fP: Exercise judicious use of this option, especially on Windows. A rogue server could send you the name of a DLL or other file that could be loaded automatically by Windows or some third party software. Providing \fI\-\-remote\-header\-name\fP multiple times has no extra effect. Disable it again with \-\-no-remote-header-name. Example: .nf curl -OJ https://example.com/file .fi See also \fI\-\-remote\-name\fP. .IP "\-O, \-\-remote\-name" Write output to a local file named like the remote file we get. (Only the file part of the remote file is used, the path is cut off.) The file is saved in the current working directory. If you want the file saved in a different directory, make sure you change the current working directory before invoking curl with this option or use \fI\-\-output\-dir\fP. The remote filename to use for saving is extracted from the given URL, nothing else, and if it already exists it is overwritten. If you want the server to be able to choose the filename refer to \fI\-\-remote\-header\-name\fP which can be used in addition to this option. If the server chooses a filename and that name already exists it is not overwritten. There is no URL decoding done on the filename. If it has %20 or other URL encoded parts of the name, they end up as\-is as filename. You may use this option as many times as the number of URLs you have. Before curl 8.10.0, curl returned an error if the URL ended with a slash, which means that there is no filename part in the URL. Starting in 8.10.0, curl sets the filename to the last directory part of the URL or if that also is missing to "curl_response" (without extension) for this situation. \fI\-\-remote\-name\fP is associated with a single URL. Use it once per URL when you use several URLs in a command line. Examples: .nf curl -O https://example.com/filename curl -O https://example.com/filename -O https://example.com/file2 .fi See also \fI\-\-remote\-name\-all\fP, \fI\-\-output\-dir\fP and \fI\-\-remote\-header\-name\fP. .IP "\-\-remote\-name\-all" Change the default action for all given URLs to be dealt with as if \fI\-\-remote\-name\fP were used for each one. If you want to disable that for a specific URL after \fI\-\-remote\-name\-all\fP has been used, you must use "\-o \-" or \fI\-\-no\-remote\-name\fP. Providing \fI\-\-remote\-name\-all\fP multiple times has no extra effect. Disable it again with \-\-no-remote-name-all. Example: .nf curl --remote-name-all ftp://example.com/file1 ftp://example.com/file2 .fi See also \fI\-\-remote\-name\fP. .IP "\-R, \-\-remote\-time" Make curl attempt to figure out the timestamp of the remote file that is getting downloaded, and if that is available make the local file get that same timestamp. Providing \fI\-\-remote\-time\fP multiple times has no extra effect. Disable it again with \-\-no-remote-time. Example: .nf curl --remote-time -o foo https://example.com .fi See also \fI\-\-remote\-name\fP and \fI\-\-time\-cond\fP. .IP "\-\-remove\-on\-error" Remove the output file if an error occurs. If curl returns an error when told to save output in a local file. This prevents curl from leaving a partial file in the case of an error during transfer. If the output is not a regular file, this option has no effect. The \fI\-\-continue\-at\fP option cannot be used together with \fI\-\-remove\-on\-error\fP. Providing \fI\-\-remove\-on\-error\fP multiple times has no extra effect. Disable it again with \-\-no-remove-on-error. Example: .nf curl --remove-on-error -o output https://example.com .fi Added in 7.83.0. See also \fI\-\-fail\fP. .IP "\-X, \-\-request <method>" Change the method to use when starting the transfer. curl passes on the verbatim string you give it in the request without any filter or other safe guards. That includes white space and control characters. .RS .IP HTTP Specifies a custom request method to use when communicating with the HTTP server. The specified request method is used instead of the method otherwise used (which defaults to \fIGET\fP). Read the HTTP 1.1 specification for details and explanations. Common additional HTTP requests include \fIPUT\fP and \fIDELETE\fP, while related technologies like WebDAV offers \fIPROPFIND\fP, \fICOPY\fP, \fIMOVE\fP and more. Normally you do not need this option. All sorts of \fIGET\fP, \fIHEAD\fP, \fIPOST\fP and \fIPUT\fP requests are rather invoked by using dedicated command line options. This option only changes the actual word used in the HTTP request, it does not alter the way curl behaves. For example if you want to make a proper HEAD request, using \-X HEAD does not suffice. You need to use the \fI\-\-head\fP option. If \fI\-\-location\fP is used, the method string you set with \fI\-\-request\fP is used for all requests, which may cause unintended side\-effects when curl does not change request method according to the HTTP 30x response codes \- and similar. Consider using \fI\-\-follow\fP instead in combination with \fI\-\-request\fP. .IP FTP Specifies a custom FTP command to use instead of \fILIST\fP when doing file lists with FTP. .IP POP3 Specifies a custom POP3 command to use instead of \fILIST\fP or \fIRETR\fP. .IP IMAP Specifies a custom IMAP command to use instead of \fILIST\fP. .IP SMTP Specifies a custom SMTP command to use instead of \fIHELP\fP or \fBVRFY\fP. .RE .IP If \fI\-\-request\fP is provided several times, the last set value is used. Examples: .nf curl --request "DELETE" https://example.com curl -X NLST ftp://example.com/ .fi See also \fI\-\-request\-target\fP and \fI\-\-follow\fP. .IP "\-\-request\-target <path>" (HTTP) Use an alternative target (path) instead of using the path as provided in the URL. Particularly useful when wanting to issue HTTP requests without leading slash or other data that does not follow the regular URL pattern, like \&"OPTIONS *". curl passes on the verbatim string you give it in the request without any filter or other safe guards. That includes white space and control characters. If \fI\-\-request\-target\fP is provided several times, the last set value is used. Example: .nf curl --request-target "*" -X OPTIONS https://example.com .fi See also \fI\-\-request\fP. .IP "\-\-resolve <[+]host:port:addr[,addr]...>" Provide a custom address for a specific host and port pair. Using this, you can make the curl requests(s) use a specified address and prevent the otherwise normally resolved address to be used. Consider it a sort of /etc/hosts alternative provided on the command line. The port number should be the number used for the specific protocol the host is used for. It means you need several entries if you want to provide addresses for the same host but different ports. By specifying "*" as host you can tell curl to resolve any host and specific port pair to the specified address. Wildcard is resolved last so any \fI\-\-resolve\fP with a specific host and port is used first. The provided address set by this option is used even if \fI\-\-ipv4\fP or \fI\-\-ipv6\fP is set to make curl use another IP version. By prefixing the host with a \(aq+\(aq you can make the entry time out after curl\(aqs default timeout (1 minute). Note that this only makes sense for long running parallel transfers with a lot of files. In such cases, if this option is used curl tries to resolve the host as it normally would once the timeout has expired. Provide IPv6 addresses within [brackets]. To redirect connects from a specific hostname or any hostname, independently of port number, consider the \fI\-\-connect\-to\fP option. Support for resolving with wildcard was added in 7.64.0. Support for the \(aq+\(aq prefix was added in 7.75.0. Support for specifying the host component as an IPv6 address was added in 8.13.0. \fI\-\-resolve\fP can be used several times in a command line. Examples: .nf curl --resolve example.com:443:127.0.0.1 https://example.com curl --resolve example.com:443:[2001:db8::252f:efd6] https://example.com .fi See also \fI\-\-connect\-to\fP and \fI\-\-alt\-svc\fP. .IP "\-\-retry <num>" If a transient error is returned when curl tries to perform a transfer, it retries this number of times before giving up. Setting the number to 0 makes curl do no retries (which is the default). Transient error means either: a timeout, an FTP 4xx response code or an HTTP 408, 429, 500, 502, 503, 504, 522 or 524 response code. When curl is about to retry a transfer, it first waits one second and then for all forthcoming retries it doubles the waiting time until it reaches 10 minutes, which then remains the set fixed delay time between the rest of the retries. By using \fI\-\-retry\-delay\fP you disable this exponential backoff algorithm. See also \fI\-\-retry\-max\-time\fP to limit the total time allowed for retries. curl complies with the Retry\-After: response header if one was present to know when to issue the next retry (added in 7.66.0). If \fI\-\-retry\fP is provided several times, the last set value is used. Example: .nf curl --retry 7 https://example.com .fi See also \fI\-\-retry\-max\-time\fP, \fI\-\-retry\-connrefused\fP and \fI\-\-retry\-delay\fP. .IP "\-\-retry\-all\-errors" Retry on any error. This option is used together with \fI\-\-retry\fP. This option is the "sledgehammer" of retrying. Do not use this option by default (for example in your \fBcurlrc\fP), there may be unintended consequences such as sending or receiving duplicate data. Do not use with redirected input or output. You might be better off handling your unique problems in a shell script. Please read the example below. \fBWARNING\fP: For server compatibility curl attempts to retry failed flaky transfers as close as possible to how they were started, but this is not possible with redirected input or output. For example, before retrying it removes output data from a failed partial transfer that was written to an output file. However this is not true of data redirected to a | pipe or > file, which are not reset. We strongly suggest you do not parse or record output via redirect in combination with this option, since you may receive duplicate data. By default curl does not return an error for transfers with an HTTP response code that indicates an HTTP error, if the transfer was successful. For example, if a server replies 404 Not Found and the reply is fully received then that is not an error. When \fI\-\-retry\fP is used then curl retries on some HTTP response codes that indicate transient HTTP errors, but that does not include most 4xx response codes such as 404. If you want to retry on all response codes that indicate HTTP errors (4xx and 5xx) then combine with \fI\-\-fail\fP. Providing \fI\-\-retry\-all\-errors\fP multiple times has no extra effect. Disable it again with \-\-no-retry-all-errors. Example: .nf curl --retry 5 --retry-all-errors https://example.com .fi Added in 7.71.0. See also \fI\-\-retry\fP. .IP "\-\-retry\-connrefused" In addition to the other conditions, also consider ECONNREFUSED as a transient error for \fI\-\-retry\fP. This option is used together with \fI\-\-retry\fP. Normally, a refused connection is not considered a transient error and therefore would not otherwise trigger a retry. Providing \fI\-\-retry\-connrefused\fP multiple times has no extra effect. Disable it again with \-\-no-retry-connrefused. Example: .nf curl --retry-connrefused --retry 7 https://example.com .fi See also \fI\-\-retry\fP and \fI\-\-retry\-all\-errors\fP. .IP "\-\-retry\-delay <seconds>" Make curl sleep this amount of time before each retry when a transfer has failed with a transient error (it changes the default backoff time algorithm between retries). This option is only interesting if \fI\-\-retry\fP is also used. Setting this delay to zero makes curl use the default backoff time. By default, curl uses an exponentially increasing timeout between retries. Starting in curl 8.16.0, this option accepts a time as decimal number for parts of seconds. The decimal value needs to be provided using a dot (.) as decimal separator \- not the local version even if it might be using another separator. If \fI\-\-retry\-delay\fP is provided several times, the last set value is used. Example: .nf curl --retry-delay 5 --retry 7 https://example.com .fi See also \fI\-\-retry\fP and \fI\-\-retry\-max\-time\fP. .IP "\-\-retry\-max\-time <seconds>" The retry timer is reset before the first transfer attempt. Retries are done as usual (see \fI\-\-retry\fP) as long as the timer has not reached this given limit. Notice that if the timer has not reached the limit, the request is made and while performing, it may take longer than this given time period. To limit a single request\(aqs maximum time, use \fI\-\-max\-time\fP. Set this option to zero to not timeout retries. The retry timer starts immediately before the first transfer attempt and includes time spent sleeping between retries (such as delays defined by \fI\-\-retry\-delay\fP). Before each new retry is started, curl checks whether the elapsed time has reached the specified limit. If it has, no further retries are performed. A transfer that has already started is allowed to run to completion even if this makes the total wall clock time exceed the limit. Use \fI\-\-max\-time\fP to also cap the duration of each individual transfer attempt. Starting in curl 8.16.0, this option accepts a time as decimal number for parts of seconds. The decimal value needs to be provided using a dot (.) as decimal separator \- not the local version even if it might be using another separator. If \fI\-\-retry\-max\-time\fP is provided several times, the last set value is used. Example: .nf curl --retry-max-time 30 --retry 10 https://example.com .fi See also \fI\-\-retry\fP and \fI\-\-retry\-delay\fP. .IP "\-\-sasl\-authzid <identity>" (LDAP IMAP POP3 SMTP) Use this authorization identity (\fBauthzid\fP), during SASL PLAIN authentication, in addition to the authentication identity (\fBauthcid\fP) as specified by \fI\-\-user\fP. If the option is not specified, the server derives the \fBauthzid\fP from the \fBauthcid\fP, but if specified, and depending on the server implementation, it may be used to access another user\(aqs inbox, that the user has been granted access to, or a shared mailbox for example. If \fI\-\-sasl\-authzid\fP is provided several times, the last set value is used. Example: .nf curl --sasl-authzid zid imap://example.com/ .fi Added in 7.66.0. See also \fI\-\-login\-options\fP. .IP "\-\-sasl\-ir" (LDAP IMAP POP3 SMTP) Enable initial response in SASL authentication. Such an "initial response" is a message sent by the client to the server after the client selects an authentication mechanism. Providing \fI\-\-sasl\-ir\fP multiple times has no extra effect. Disable it again with \-\-no-sasl-ir. Example: .nf curl --sasl-ir imap://example.com/ .fi See also \fI\-\-sasl\-authzid\fP. .IP "\-\-service\-name <name>" Set the service name for SPNEGO. If \fI\-\-service\-name\fP is provided several times, the last set value is used. Example: .nf curl --service-name sockd/server https://example.com .fi See also \fI\-\-negotiate\fP and \fI\-\-proxy\-service\-name\fP. .IP "\-S, \-\-show\-error" When used with \fI\-\-silent\fP, it makes curl show an error message if it fails. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-show\-error\fP multiple times has no extra effect. Disable it again with \-\-no-show-error. Example: .nf curl --show-error --silent https://example.com .fi See also \fI\-\-no\-progress\-meter\fP. .IP "\-i, \-\-show\-headers" (HTTP FTP) Show response headers in the output. HTTP response headers can include things like server name, cookies, date of the document, HTTP version and more. With non\-HTTP protocols, the "headers" are other server communication. This option makes the response headers get saved in the same stream/output as the data. \fI\-\-dump\-header\fP exists to save headers in a separate stream. When HTTP headers are output to a tty, curl may use escape codes to make the header field names appear in bold and URLs in "Location:" headers be especially marked as such. Disable the use of terminal escape codes with \fI\-\-no\-styled\-output\fP. (This means using the \fI\-\-styled\-output\fP option with a \&"\fI\-\-no\-\fP" prefix to disable it.) To view the request headers, consider the \fI\-\-verbose\fP option. Prior to 7.75.0 curl did not print the headers if \fI\-\-fail\fP was used in combination with this option and there was an error reported by the server. This option was called \fI\-\-include\fP before 8.10.0. The previous name remains functional. Providing \fI\-\-show\-headers\fP multiple times has no extra effect. Disable it again with \-\-no-show-headers. Example: .nf curl -i https://example.com .fi See also \fI\-\-verbose\fP and \fI\-\-dump\-header\fP. .IP "\-\-sigalgs <list>" (TLS) Set specific signature algorithms to use during SSL session establishment according to RFC 5246, 7.4.1.4.1. An algorithm can use either a signature algorithm and a hash algorithm pair separated by a \&"+" (e.g. "ECDSA+SHA224"), or its TLS 1.3 signature scheme name (e.g. "ed25519"). Multiple algorithms can be provided by separating them with ":" (e.g. "DSA+SHA256:rsa_pss_pss_sha256"). The parameter is available as "\-sigalgs" in the OpenSSL "s_client" and "s_server" utilities. \&"\fI\-\-sigalgs\fP" allows a OpenSSL powered curl to make SSL\-connections with exactly the signature algorithms requested by the client, avoiding nontransparent client/server negotiations. If this option is set, the default signature algorithm list built into OpenSSL are ignored. If \fI\-\-sigalgs\fP is provided several times, the last set value is used. Example: .nf curl --sigalgs ecdsa_secp256r1_sha256 https://example.com .fi Added in 8.14.0. See also \fI\-\-ciphers\fP. .IP "\-s, \-\-silent" Silent or quiet mode. Do not show progress meter, warning messages or error messages. Makes curl mute. It still outputs the data you ask for, potentially even to the terminal/stdout unless you redirect it. Use \fI\-\-show\-error\fP in addition to this option to disable progress meter but still show error messages. Providing \fI\-\-silent\fP multiple times has no extra effect. Disable it again with \-\-no-silent. Example: .nf curl -s https://example.com .fi See also \fI\-\-verbose\fP, \fI\-\-stderr\fP and \fI\-\-no\-progress\-meter\fP. .IP "\-\-skip\-existing" If there is a local file present when a download is requested, the operation is skipped. Note that curl cannot know if the local file was previously downloaded fine, or if it is incomplete etc, it knows if there is a filename present in the file system or not and it skips the transfer if it is. Providing \fI\-\-skip\-existing\fP multiple times has no extra effect. Disable it again with \-\-no-skip-existing. Example: .nf curl --skip-existing --output local/dir/file https://example.com .fi Added in 8.10.0. See also \fI\-\-output\fP, \fI\-\-remote\-name\fP and \fI\-\-no\-clobber\fP. .IP "\-\-socks4 <host[:port]>" Use the specified SOCKS4 proxy. If the port number is not specified, it is assumed at port 1080. Using this socket type makes curl resolve the hostname and pass the address on to the proxy. To specify the proxy on a Unix domain socket, use localhost for host and append the absolute path to the domain socket. For example: \&"socks4://localhost/path/to/socket.sock" (the scheme may be omitted). This option overrides any previous use of \fI\-\-proxy\fP, as they are mutually exclusive. This option is superfluous since you can specify a socks4 proxy with \fI\-\-proxy\fP using a "socks4://" protocol prefix. \fI\-\-preproxy\fP can be used to specify a SOCKS proxy at the same time proxy is used with an HTTP/HTTPS proxy. In such a case, curl first connects to the SOCKS proxy and then connects (through SOCKS) to the HTTP or HTTPS proxy. If \fI\-\-socks4\fP is provided several times, the last set value is used. Example: .nf curl --socks4 hostname:4096 https://example.com .fi This option is mutually exclusive with \fI\-\-proxy\fP, \fI\-\-socks4a\fP, \fI\-\-socks5\fP and \fI\-\-socks5\-hostname\fP. See also \fI\-\-socks4a\fP, \fI\-\-socks5\fP and \fI\-\-socks5\-hostname\fP. .IP "\-\-socks4a <host[:port]>" Use the specified SOCKS4a proxy. If the port number is not specified, it is assumed at port 1080. This asks the proxy to resolve the hostname. To specify the proxy on a Unix domain socket, use localhost for host and append the absolute path to the domain socket. For example: \&"socks4a://localhost/path/to/socket.sock" (the scheme may be omitted). This option overrides any previous use of \fI\-\-proxy\fP, as they are mutually exclusive. This option is superfluous since you can specify a socks4a proxy with \fI\-\-proxy\fP using a "socks4a://" protocol prefix. \fI\-\-preproxy\fP can be used to specify a SOCKS proxy at the same time \fI\-\-proxy\fP is used with an HTTP/HTTPS proxy. In such a case, curl first connects to the SOCKS proxy and then connects (through SOCKS) to the HTTP or HTTPS proxy. If \fI\-\-socks4a\fP is provided several times, the last set value is used. Example: .nf curl --socks4a hostname:4096 https://example.com .fi This option is mutually exclusive with \fI\-\-proxy\fP, \fI\-\-socks4\fP, \fI\-\-socks5\fP and \fI\-\-socks5\-hostname\fP. See also \fI\-\-socks4\fP, \fI\-\-socks5\fP and \fI\-\-socks5\-hostname\fP. .IP "\-\-socks5 <host[:port]>" Use the specified SOCKS5 proxy \- but resolve the hostname locally. If the port number is not specified, it is assumed at port 1080. To specify the proxy on a Unix domain socket, use localhost for host and append the absolute path to the domain socket. For example: \&"socks5://localhost/path/to/socket.sock" (the scheme may be omitted). This option overrides any previous use of \fI\-\-proxy\fP, as they are mutually exclusive. This option is superfluous since you can specify a socks5 proxy with \fI\-\-proxy\fP using a "socks5://" protocol prefix. \fI\-\-preproxy\fP can be used to specify a SOCKS proxy at the same time \fI\-\-proxy\fP is used with an HTTP/HTTPS proxy. In such a case, curl first connects to the SOCKS proxy and then connects (through SOCKS) to the HTTP or HTTPS proxy. This option does not work with FTPS or LDAP. If \fI\-\-socks5\fP is provided several times, the last set value is used. Examples: .nf curl --socks5 proxy.example:7000 https://example.com curl --socks5 localhost/path/unix-domain https://example.com .fi This option is mutually exclusive with \fI\-\-proxy\fP, \fI\-\-socks4\fP, \fI\-\-socks4a\fP and \fI\-\-socks5\-hostname\fP. See also \fI\-\-socks5\-hostname\fP and \fI\-\-socks4a\fP. .IP "\-\-socks5\-basic" Use username/password authentication when connecting to a SOCKS5 proxy. The username/password authentication is enabled by default. Use \fI\-\-socks5\-gssapi\fP to force GSS\-API authentication to SOCKS5 proxies. Providing \fI\-\-socks5\-basic\fP multiple times has no extra effect. Example: .nf curl --socks5-basic --socks5 hostname:4096 https://example.com .fi See also \fI\-\-socks5\fP. .IP "\-\-socks5\-gssapi" (GSS/kerberos) Use GSS\-API authentication when connecting to a SOCKS5 proxy. The GSS\-API authentication is enabled by default (if curl is compiled with GSS\-API support). Use \fI\-\-socks5\-basic\fP to force username/password authentication to SOCKS5 proxies. Providing \fI\-\-socks5\-gssapi\fP multiple times has no extra effect. Disable it again with \-\-no-socks5-gssapi. Example: .nf curl --socks5-gssapi --socks5 hostname:4096 https://example.com .fi See also \fI\-\-socks5\fP. .IP "\-\-socks5\-gssapi\-nec" (GSS/kerberos) As part of the GSS\-API negotiation a protection mode is negotiated. RFC 1961 says in section 4.3/4.4 it should be protected, but the NEC reference implementation does not. The option \fI\-\-socks5\-gssapi\-nec\fP allows the unprotected exchange of the protection mode negotiation. Providing \fI\-\-socks5\-gssapi\-nec\fP multiple times has no extra effect. Disable it again with \-\-no-socks5-gssapi-nec. Example: .nf curl --socks5-gssapi-nec --socks5 hostname:4096 https://example.com .fi See also \fI\-\-socks5\fP. .IP "\-\-socks5\-gssapi\-service <name>" Set the service name for a socks server. Default is \fBrcmd/server\-fqdn\fP. If \fI\-\-socks5\-gssapi\-service\fP is provided several times, the last set value is used. Example: .nf curl --socks5-gssapi-service sockd --socks5 hostname:4096 https://example.com .fi See also \fI\-\-socks5\fP. .IP "\-\-socks5\-hostname <host[:port]>" Use the specified SOCKS5 proxy (and let the proxy resolve the hostname). If the port number is not specified, it is assumed at port 1080. To specify the proxy on a Unix domain socket, use localhost for host and append the absolute path to the domain socket. For example: \&"socks5h://localhost/path/to/socket.sock" (the scheme may be omitted). This option overrides any previous use of \fI\-\-proxy\fP, as they are mutually exclusive. This option is superfluous since you can specify a socks5 hostname proxy with \fI\-\-proxy\fP using a "socks5h://" protocol prefix. \fI\-\-preproxy\fP can be used to specify a SOCKS proxy at the same time \fI\-\-proxy\fP is used with an HTTP/HTTPS proxy. In such a case, curl first connects to the SOCKS proxy and then connects (through SOCKS) to the HTTP or HTTPS proxy. If \fI\-\-socks5\-hostname\fP is provided several times, the last set value is used. Example: .nf curl --socks5-hostname proxy.example:7000 https://example.com .fi This option is mutually exclusive with \fI\-\-proxy\fP, \fI\-\-socks4\fP, \fI\-\-socks4a\fP and \fI\-\-socks5\fP. See also \fI\-\-socks5\fP and \fI\-\-socks4a\fP. .IP "\-Y, \-\-speed\-limit <speed>" If a transfer is slower than this set speed (in bytes per second) for a given number of seconds, it gets aborted. The time period is set with \fI\-\-speed\-time\fP and is 30 seconds by default. If \fI\-\-speed\-limit\fP is provided several times, the last set value is used. Example: .nf curl --speed-limit 300 --speed-time 10 https://example.com .fi See also \fI\-\-speed\-time\fP, \fI\-\-limit\-rate\fP and \fI\-\-max\-time\fP. .IP "\-y, \-\-speed\-time <seconds>" If a transfer runs slower than speed\-limit bytes per second during a speed\-time period, the transfer is aborted. If speed\-time is used, the default speed\-limit is 1 unless set with \fI\-\-speed\-limit\fP. This option controls transfers (in both directions) but does not affect slow connects etc. If this is a concern for you, try the \fI\-\-connect\-timeout\fP option. If \fI\-\-speed\-time\fP is provided several times, the last set value is used. Example: .nf curl --speed-limit 300 --speed-time 10 https://example.com .fi See also \fI\-\-speed\-limit\fP and \fI\-\-limit\-rate\fP. .IP "\-\-ssl" (FTP IMAP POP3 SMTP LDAP) Warning: this is considered an insecure option. Consider using \fI\-\-ssl\-reqd\fP instead to be sure curl upgrades to a secure connection. Try to use SSL/TLS for the connection \- often referred to as STARTTLS or STLS because of the involved commands. Reverts to a non\-secure connection if the server does not support SSL/TLS. See also \fI\-\-ftp\-ssl\-control\fP and \fI\-\-ssl\-reqd\fP for different levels of encryption required. This option is handled in LDAP (added in 7.81.0). It is fully supported by the OpenLDAP backend and ignored by the generic ldap backend. Please note that a server may close the connection if the negotiation fails. If set, this option overrides \fI\-\-ftp\-ssl\-control\fP. This option was formerly known as \fI\-\-ftp\-ssl\fP. That option name can still be used but might be removed in a future version. Providing \fI\-\-ssl\fP multiple times has no extra effect. Disable it again with \-\-no-ssl. Example: .nf curl --ssl pop3://example.com/ .fi See also \fI\-\-ssl\-reqd\fP, \fI\-\-insecure\fP and \fI\-\-ciphers\fP. .IP "\-\-ssl\-allow\-beast" (TLS) Do not work around a security flaw in the TLS1.0 protocol known as BEAST. If this option is not used, the TLS layer may use workarounds known to cause interoperability problems with some older server implementations. This option only changes how curl does TLS 1.0 and has no effect on later TLS versions. \fBWARNING\fP: this option loosens the TLS security, and by using this flag you ask for exactly that. Providing \fI\-\-ssl\-allow\-beast\fP multiple times has no extra effect. Disable it again with \-\-no-ssl-allow-beast. Example: .nf curl --ssl-allow-beast https://example.com .fi See also \fI\-\-proxy\-ssl\-allow\-beast\fP and \fI\-\-insecure\fP. .IP "\-\-ssl\-auto\-client\-cert" (TLS) (Schannel) Automatically locate and use a client certificate for authentication, when requested by the server. Since the server can request any certificate that supports client authentication in the OS certificate store it could be a privacy violation and unexpected. Providing \fI\-\-ssl\-auto\-client\-cert\fP multiple times has no extra effect. Disable it again with \-\-no-ssl-auto-client-cert. Example: .nf curl --ssl-auto-client-cert https://example.com .fi Added in 7.77.0. See also \fI\-\-proxy\-ssl\-auto\-client\-cert\fP. .IP "\-\-ssl\-no\-revoke" (TLS) (Schannel) Disable certificate revocation checks. WARNING: this option loosens the SSL security, and by using this flag you ask for exactly that. Providing \fI\-\-ssl\-no\-revoke\fP multiple times has no extra effect. Disable it again with \-\-no-ssl-no-revoke. Example: .nf curl --ssl-no-revoke https://example.com .fi See also \fI\-\-crlfile\fP. .IP "\-\-ssl\-reqd" (FTP IMAP POP3 SMTP LDAP) Require SSL/TLS for the connection \- often referred to as STARTTLS or STLS because of the involved commands. Terminates the connection if the transfer cannot be upgraded to use SSL/TLS. This option is handled in LDAP (added in 7.81.0). It is fully supported by the OpenLDAP backend and rejected by the generic ldap backend if explicit TLS is required. This option is unnecessary if you use a URL scheme that in itself implies immediate and implicit use of TLS, like for FTPS, IMAPS, POP3S, SMTPS and LDAPS. Such a transfer always fails if the TLS handshake does not work. This option was formerly known as \fI\-\-ftp\-ssl\-reqd\fP. Providing \fI\-\-ssl\-reqd\fP multiple times has no extra effect. Disable it again with \-\-no-ssl-reqd. Example: .nf curl --ssl-reqd ftp://example.com .fi See also \fI\-\-ssl\fP and \fI\-\-insecure\fP. .IP "\-\-ssl\-revoke\-best\-effort" (TLS) (Schannel) Ignore certificate revocation checks when they failed due to missing/offline distribution points for the revocation check lists. Providing \fI\-\-ssl\-revoke\-best\-effort\fP multiple times has no extra effect. Disable it again with \-\-no-ssl-revoke-best-effort. Example: .nf curl --ssl-revoke-best-effort https://example.com .fi Added in 7.70.0. See also \fI\-\-crlfile\fP and \fI\-\-insecure\fP. .IP "\-\-ssl\-sessions <filename>" (TLS) **WARNING**: this option is experimental. Do not use in production. Use the given file to load SSL session tickets into curl\(aqs cache before starting any transfers. At the end of a successful curl run, the cached SSL sessions tickets are saved to the file, replacing any previous content. The file does not have to exist, but curl reports an error if it is unable to create it. Unused loaded tickets are saved again, unless they get replaced or purged from the cache for space reasons. Using a session file allows "\fI\-\-tls\-earlydata\fP" to send the first request in "0\-RTT" mode, should an SSL session with the feature be found. Note that a server may not support early data. Also note that early data does not provide forward secrecy, e.g. is not as secure. The SSL session tickets are stored as base64 encoded text, each ticket on its own line. The hostnames are cryptographically salted and hashed. While this prevents someone from easily seeing the hosts you contacted, they could still check if a specific hostname matches one of the values. This feature requires that the underlying libcurl was built with the experimental SSL session import/export feature (SSLS\-EXPORT) enabled. If \fI\-\-ssl\-sessions\fP is provided several times, the last set value is used. Example: .nf curl --ssl-sessions sessions.txt https://example.com .fi Added in 8.12.0. See also \fI\-\-tls\-earlydata\fP. .IP "\-2, \-\-sslv2" (SSL) This option previously asked curl to use SSLv2, but is now ignored (added in 7.77.0). SSLv2 is widely considered insecure (see RFC 6176). Providing \fI\-\-sslv2\fP multiple times has no extra effect. Example: .nf curl --sslv2 https://example.com .fi For \fI\-\-sslv2\fP to work, it requires that the underlying libcurl is built to support TLS. This option is mutually exclusive with \fI\-\-sslv3\fP, \fI\-\-tlsv1\fP, \fI\-\-tlsv1.1\fP and \fI\-\-tlsv1.2\fP. See also \fI\-\-http1.1\fP and \fI\-\-http2\fP. .IP "\-3, \-\-sslv3" (SSL) This option previously asked curl to use SSLv3, but is now ignored (added in 7.77.0). SSLv3 is widely considered insecure (see RFC 7568). Providing \fI\-\-sslv3\fP multiple times has no extra effect. Example: .nf curl --sslv3 https://example.com .fi For \fI\-\-sslv3\fP to work, it requires that the underlying libcurl is built to support TLS. This option is mutually exclusive with \fI\-\-sslv2\fP, \fI\-\-tlsv1\fP, \fI\-\-tlsv1.1\fP and \fI\-\-tlsv1.2\fP. See also \fI\-\-http1.1\fP and \fI\-\-http2\fP. .IP "\-\-stderr <file>" Redirect all writes to stderr to the specified file instead. If the filename is a plain \(aq\-\(aq, it is instead written to stdout. This option is global and does not need to be specified for each use of \fI\-\-next\fP. If \fI\-\-stderr\fP is provided several times, the last set value is used. Example: .nf curl --stderr output.txt https://example.com .fi See also \fI\-\-verbose\fP and \fI\-\-silent\fP. .IP "\-\-styled\-output" Enable automatic use of bold font styles when writing HTTP headers to the terminal. Use \fI\-\-no\-styled\-output\fP to switch them off. Styled output requires a terminal that supports bold fonts. This feature is not present on curl for Windows due to lack of this capability. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-styled\-output\fP multiple times has no extra effect. Disable it again with \-\-no-styled-output. Example: .nf curl --styled-output -I https://example.com .fi See also \fI\-\-head\fP and \fI\-\-verbose\fP. .IP "\-\-suppress\-connect\-headers" When \fI\-\-proxytunnel\fP is used and a CONNECT request is made, do not output proxy CONNECT response headers. This option is meant to be used with \fI\-\-dump\-header\fP or \fI\-\-show\-headers\fP which are used to show protocol headers in the output. It has no effect on debug options such as \fI\-\-verbose\fP or \fI\-\-trace\fP, or any statistics. Providing \fI\-\-suppress\-connect\-headers\fP multiple times has no extra effect. Disable it again with \-\-no-suppress-connect-headers. Example: .nf curl --suppress-connect-headers --show-headers -x proxy https://example.com .fi See also \fI\-\-dump\-header\fP, \fI\-\-show\-headers\fP and \fI\-\-proxytunnel\fP. .IP "\-\-tcp\-fastopen" Enable use of TCP Fast Open (RFC 7413). TCP Fast Open is a TCP extension that allows data to be sent earlier over the connection (before the final handshake ACK) if the client and server have been connected previously. Providing \fI\-\-tcp\-fastopen\fP multiple times has no extra effect. Disable it again with \-\-no-tcp-fastopen. Example: .nf curl --tcp-fastopen https://example.com .fi See also \fI\-\-false\-start\fP. .IP "\-\-tcp\-nodelay" Turn on the TCP_NODELAY option. This option disables the Nagle algorithm on TCP connections. The purpose of this algorithm is to minimize the number of small packets on the network (where "small packets" means TCP segments less than the Maximum Segment Size for the network). Maximizing the amount of data sent per TCP segment is good because it amortizes the overhead of the send. In some cases small segments may need to be sent without delay. This is less efficient than sending larger amounts of data at a time, and can contribute to congestion on the network if overdone. curl sets this option by default and you need to explicitly switch it off if you do not want it on. Providing \fI\-\-tcp\-nodelay\fP multiple times has no extra effect. Disable it again with \-\-no-tcp-nodelay. Example: .nf curl --tcp-nodelay https://example.com .fi See also \fI\-\-no\-buffer\fP. .IP "\-t, \-\-telnet\-option <opt=val>" (TELNET) Pass options to the telnet protocol. Supported options are: .RS .IP TTYPE=<term> Sets the terminal type. .IP "XDISPLOC=<X display>" Sets the X display location. .IP NEW_ENV=<var,val> Sets an environment variable. .RE .IP \fI\-\-telnet\-option\fP can be used several times in a command line. Example: .nf curl -t TTYPE=vt100 telnet://example.com/ .fi See also \fI\-\-config\fP. .IP "\-\-tftp\-blksize <value>" (TFTP) Set the TFTP \fBBLKSIZE\fP option (must be 512 or larger). This is the block size that curl tries to use when transferring data to or from a TFTP server. By default 512 bytes are used. If \fI\-\-tftp\-blksize\fP is provided several times, the last set value is used. Example: .nf curl --tftp-blksize 1024 tftp://example.com/file .fi See also \fI\-\-tftp\-no\-options\fP. .IP "\-\-tftp\-no\-options" (TFTP) Do not send TFTP options requests. This improves interop with some legacy servers that do not acknowledge or properly implement TFTP options. When this option is used \fI\-\-tftp\-blksize\fP is ignored. Providing \fI\-\-tftp\-no\-options\fP multiple times has no extra effect. Disable it again with \-\-no-tftp-no-options. Example: .nf curl --tftp-no-options tftp://192.168.0.1/ .fi See also \fI\-\-tftp\-blksize\fP. .IP "\-z, \-\-time\-cond <time>" (HTTP FTP) Request a file that has been modified later than the given time and date, or one that has been modified before that time. The date expression can be all sorts of date strings or if it does not match any internal ones, it is treated as a filename and curl tries to get the modification date (mtime) from that file instead. See the \fIcurl_getdate(3)\fP man page for date expression details. Start the date expression with a dash (\-) to make it request for a document that is older than the given date/time, default is a document that is newer than the specified date/time. If provided a non\-existing file, curl outputs a warning about that fact and proceeds to do the transfer without a time condition. If \fI\-\-time\-cond\fP is provided several times, the last set value is used. Examples: .nf curl -z "Wed 01 Sep 2021 12:18:00" https://example.com curl -z "-Wed 01 Sep 2021 12:18:00" https://example.com curl -z file https://example.com .fi See also \fI\-\-etag\-compare\fP and \fI\-\-remote\-time\fP. .IP "\-\-tls\-earlydata" (TLS) Enable the use of TLSv1.3 early data, also known as \(aq0RTT\(aq where possible. This has security implications for the requests sent that way. This option can be used when curl is built to use GnuTLS, OpenSSL, quictls and wolfSSL as a TLS provider (but not AWS\-LC, BoringSSL, or Rustls). If a server supports this TLSv1.3 feature, and to what extent, is announced as part of the TLS "session" sent back to curl. Until curl has seen such a session in a previous request, early data cannot be used. When a new connection is initiated with a known TLSv1.3 session, and that session announced early data support, the first request on this connection is sent \fIbefore\fP the TLS handshake is complete. While the early data is also encrypted, it is not protected against replays. An attacker can send your early data to the server again and the server would accept it. If your request contacts a public server and only retrieves a file, there may be no harm in that. If the first request orders a refrigerator for you, it is probably not a good idea to use early data for it. curl cannot deduce what the security implications of your requests actually are and make this decision for you. The amount of early data sent can be inspected by using the "\fI\-\-write\-out\fP" variable "tls_earlydata". \fBWARNING\fP: this option has security implications. See above for more details. Providing \fI\-\-tls\-earlydata\fP multiple times has no extra effect. Disable it again with \-\-no-tls-earlydata. Example: .nf curl --tls-earlydata https://example.com .fi Added in 8.11.0. See also \fI\-\-tlsv1.3\fP, \fI\-\-tls\-max\fP and \fI\-\-ssl\-sessions\fP. .IP "\-\-tls\-max <VERSION>" (TLS) Set the maximum allowed TLS version. The minimum acceptable version is set by tlsv1.0, tlsv1.1, tlsv1.2 or tlsv1.3. If the connection is done without TLS, this option has no effect. This includes QUIC\-using (HTTP/3) transfers. .RS .IP default Use up to the recommended TLS version. .IP 1.0 Use up to TLSv1.0. .IP 1.1 Use up to TLSv1.1. .IP 1.2 Use up to TLSv1.2. .IP 1.3 Use up to TLSv1.3. .RE .IP If \fI\-\-tls\-max\fP is provided several times, the last set value is used. Examples: .nf curl --tls-max 1.2 https://example.com curl --tls-max 1.3 --tlsv1.2 https://example.com .fi For \fI\-\-tls\-max\fP to work, it requires that the underlying libcurl is built to support TLS. See also \fI\-\-tlsv1.0\fP, \fI\-\-tlsv1.1\fP, \fI\-\-tlsv1.2\fP and \fI\-\-tlsv1.3\fP. .IP "\-\-tls13\-ciphers <list>" (TLS) Set which cipher suites to use in the connection if it negotiates TLS 1.3. The list of ciphers suites must specify valid ciphers. Read up on TLS 1.3 cipher suite details on this URL: https://curl.se/docs/ssl\-ciphers.html This option is used when curl is built to use OpenSSL 1.1.1 or later, wolfSSL, or mbedTLS 3.6.0 or later. Before curl 8.10.0 with mbedTLS or wolfSSL, TLS 1.3 cipher suites were set by using the \fI\-\-ciphers\fP option. If \fI\-\-tls13\-ciphers\fP is provided several times, the last set value is used. Example: .nf curl --tls13-ciphers TLS_AES_128_GCM_SHA256 https://example.com .fi See also \fI\-\-ciphers\fP, \fI\-\-proxy\-tls13\-ciphers\fP and \fI\-\-curves\fP. .IP "\-\-tlsauthtype <type>" (TLS) Set TLS authentication type. Currently, the only supported option is "SRP", for TLS\-SRP (RFC 5054). If \fI\-\-tlsuser\fP and \fI\-\-tlspassword\fP are specified but \fI\-\-tlsauthtype\fP is not, then this option defaults to "SRP". This option works only if the underlying libcurl is built with TLS\-SRP support, which requires OpenSSL or GnuTLS with TLS\-SRP support. If \fI\-\-tlsauthtype\fP is provided several times, the last set value is used. Example: .nf curl --tlsauthtype SRP https://example.com .fi See also \fI\-\-tlsuser\fP. .IP "\-\-tlspassword <string>" (TLS) Set password to use with the TLS authentication method specified with \fI\-\-tlsauthtype\fP. Requires that \fI\-\-tlsuser\fP is set. This option does not work with TLS 1.3. If \fI\-\-tlspassword\fP is provided several times, the last set value is used. Example: .nf curl --tlspassword pwd --tlsuser user https://example.com .fi See also \fI\-\-tlsuser\fP. .IP "\-\-tlsuser <name>" (TLS) Set username for use with the TLS authentication method specified with \fI\-\-tlsauthtype\fP. Requires that \fI\-\-tlspassword\fP also is set. This option does not work with TLS 1.3. If \fI\-\-tlsuser\fP is provided several times, the last set value is used. Example: .nf curl --tlspassword pwd --tlsuser user https://example.com .fi See also \fI\-\-tlspassword\fP. .IP "\-1, \-\-tlsv1" (TLS) Use at least TLS version 1.x when negotiating with a remote TLS server. That means TLS version 1.0 or higher Providing \fI\-\-tlsv1\fP multiple times has no extra effect. Example: .nf curl --tlsv1 https://example.com .fi For \fI\-\-tlsv1\fP to work, it requires that the underlying libcurl is built to support TLS. This option is mutually exclusive with \fI\-\-tlsv1.1\fP, \fI\-\-tlsv1.2\fP and \fI\-\-tlsv1.3\fP. See also \fI\-\-http1.1\fP and \fI\-\-http2\fP. .IP "\-\-tlsv1.0" (TLS) Force curl to use TLS version 1.0 or later when connecting to a remote TLS server. In old versions of curl this option was documented to allow _only_ TLS 1.0. That behavior was inconsistent depending on the TLS library. Use \fI\-\-tls\-max\fP if you want to set a maximum TLS version. Providing \fI\-\-tlsv1.0\fP multiple times has no extra effect. Example: .nf curl --tlsv1.0 https://example.com .fi See also \fI\-\-tlsv1.3\fP. .IP "\-\-tlsv1.1" (TLS) Force curl to use TLS version 1.1 or later when connecting to a remote TLS server. In old versions of curl this option was documented to allow _only_ TLS 1.1. That behavior was inconsistent depending on the TLS library. Use \fI\-\-tls\-max\fP if you want to set a maximum TLS version. Providing \fI\-\-tlsv1.1\fP multiple times has no extra effect. Example: .nf curl --tlsv1.1 https://example.com .fi See also \fI\-\-tlsv1.3\fP and \fI\-\-tls\-max\fP. .IP "\-\-tlsv1.2" (TLS) Force curl to use TLS version 1.2 or later when connecting to a remote TLS server. In old versions of curl this option was documented to allow _only_ TLS 1.2. That behavior was inconsistent depending on the TLS library. Use \fI\-\-tls\-max\fP if you want to set a maximum TLS version. Providing \fI\-\-tlsv1.2\fP multiple times has no extra effect. Example: .nf curl --tlsv1.2 https://example.com .fi See also \fI\-\-tlsv1.3\fP and \fI\-\-tls\-max\fP. .IP "\-\-tlsv1.3" (TLS) Force curl to use TLS version 1.3 or later when connecting to a remote TLS server. If the connection is done without TLS, this option has no effect. This includes QUIC\-using (HTTP/3) transfers. Note that TLS 1.3 is not supported by all TLS backends. Providing \fI\-\-tlsv1.3\fP multiple times has no extra effect. Example: .nf curl --tlsv1.3 https://example.com .fi See also \fI\-\-tlsv1.2\fP and \fI\-\-tls\-max\fP. .IP "\-\-tr\-encoding" (HTTP) Request a compressed Transfer\-Encoding response using one of the algorithms curl supports, and uncompress the data while receiving it. This method was once intended to be the way to do automatic data compression for HTTP but for all practical purposes using Content\-Encoding as done with \fI\-\-compressed\fP has superseded transfer encoding. The \fI\-\-tr\-encoding\fP option is therefore often not be one you want. Providing \fI\-\-tr\-encoding\fP multiple times has no extra effect. Disable it again with \-\-no-tr-encoding. Example: .nf curl --tr-encoding https://example.com .fi See also \fI\-\-compressed\fP. .IP "\-\-trace <file>" Save a full trace dump of all incoming and outgoing data, including descriptive information, in the given output file. Use "\-" as filename to have the output sent to stdout. Use "%" as filename to have the output sent to stderr. Note that verbose output of curl activities and network traffic might contain sensitive data, including usernames, credentials or secret data content. Be aware and be careful when sharing trace logs with others. This option is global and does not need to be specified for each use of \fI\-\-next\fP. If \fI\-\-trace\fP is provided several times, the last set value is used. Example: .nf curl --trace log.txt https://example.com .fi This option is mutually exclusive with \fI\-\-verbose\fP and \fI\-\-trace\-ascii\fP. See also \fI\-\-trace\-ascii\fP, \fI\-\-trace\-config\fP, \fI\-\-trace\-ids\fP and \fI\-\-trace\-time\fP. .IP "\-\-trace\-ascii <file>" Save a full trace dump of all incoming and outgoing data, including descriptive information, in the given output file. Use "\-" as filename to have the output sent to stdout. Use "%" as filename to send the output to stderr. This is similar to \fI\-\-trace\fP, but leaves out the hex part and only shows the ASCII part of the dump. It makes smaller output that might be easier to read for untrained humans. Note that verbose output of curl activities and network traffic might contain sensitive data, including usernames, credentials or secret data content. Be aware and be careful when sharing trace logs with others. This option is global and does not need to be specified for each use of \fI\-\-next\fP. If \fI\-\-trace\-ascii\fP is provided several times, the last set value is used. Example: .nf curl --trace-ascii log.txt https://example.com .fi This option is mutually exclusive with \fI\-\-trace\fP and \fI\-\-verbose\fP. See also \fI\-\-verbose\fP and \fI\-\-trace\fP. .IP "\-\-trace\-config <string>" Set configuration for trace output. A comma\-separated list of components where detailed output can be made available from. Names are case\-insensitive. Specify \(aqall\(aq to enable all trace components. In addition to trace component names, specify "ids" and "time" to avoid extra \fI\-\-trace\-ids\fP or \fI\-\-trace\-time\fP parameters. See the \fIcurl_global_trace(3)\fP man page for more details. This option is global and does not need to be specified for each use of \fI\-\-next\fP. \fI\-\-trace\-config\fP can be used several times in a command line. Example: .nf curl --trace-config ids,http/2 https://example.com .fi Added in 8.3.0. See also \fI\-\-verbose\fP and \fI\-\-trace\fP. .IP "\-\-trace\-ids" Prepend the transfer and connection identifiers to each trace or verbose line that curl displays. The identifiers are unique numbers assigned to each connection and transfer to allow a user to better understand which transfer and connection each verbose output line refers to. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-trace\-ids\fP multiple times has no extra effect. Disable it again with \-\-no-trace-ids. Example: .nf curl --trace-ids --trace-ascii output https://example.com .fi Added in 8.2.0. See also \fI\-\-trace\fP and \fI\-\-verbose\fP. .IP "\-\-trace\-time" Prepend a time stamp to each trace or verbose line that curl displays. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-trace\-time\fP multiple times has no extra effect. Disable it again with \-\-no-trace-time. Example: .nf curl --trace-time --trace-ascii output https://example.com .fi See also \fI\-\-trace\fP and \fI\-\-verbose\fP. .IP "\-\-unix\-socket <path>" (HTTP) Connect to the server through this Unix domain socket, instead of using the network. To connect to a proxy over Unix domain socket, see \fI\-\-proxy\fP. If \fI\-\-unix\-socket\fP is provided several times, the last set value is used. Example: .nf curl --unix-socket socket-path https://example.com .fi See also \fI\-\-abstract\-unix\-socket\fP. .IP "\-T, \-\-upload\-file <file>" Upload the specified local file to the remote URL. If there is no file part in the specified URL, curl appends the local file name to the end of the URL before the operation starts. You must use a trailing slash ("/") on the last directory to prove to curl that there is no filename or curl thinks that your last directory name is the remote filename to use. When putting the local filename at the end of the URL, curl ignores what is on the left side of any slash ("/") or backslash ("\\\\") used in the filename and only appends what is on the right side of the rightmost such character. Use the filename "\-" (a single dash) to use stdin instead of a given file. Alternately, the filename "." (a single period) may be specified instead of \&"\-" to use stdin in non\-blocking mode to allow reading server output while stdin is being uploaded. If this option is used with an HTTP(S) URL, the PUT method is used. You can specify one \fI\-\-upload\-file\fP for each URL on the command line. Each \fI\-\-upload\-file\fP + URL pair specifies what to upload and to where. curl also supports globbing of the \fI\-\-upload\-file\fP argument, meaning that you can upload multiple files to a single URL by using the same URL globbing style supported in the URL. Example: .nf curl \--upload\-file \(aqfile{1,2,3}\(aq ftp://ftp.example/ .fi Since curl 8.21.0, you can use parts of the upload filename when it uses globbing by setting a glob name and referencing that in the same way you reference named URL globs. For example, if you upload three files to a single fixed HTTP URL and want to save the corresponding responses in separate files: .nf curl \-T \(aqfile{<num>1,2,3}\(aq \\ https://upload.example/ \-o \(aqresponse\-#<num>\(aq .fi When uploading to an SMTP server (aka "sending email"): the uploaded data is assumed to be RFC 5322 formatted. It has to feature the necessary set of headers and mail body formatted correctly by the user as curl does not transcode nor encode it further in any way. \fI\-\-upload\-file\fP is associated with a single URL. Use it once per URL when you use several URLs in a command line. Examples: .nf curl -T file https://example.com curl -T "img[1-1000].png" ftp://ftp.example.com/ curl --upload-file "{file1,file2}" https://example.com curl -T file -T file2 https://example.com https://example.com .fi See also \fI\-\-get\fP, \fI\-\-head\fP, \fI\-\-request\fP and \fI\-\-data\fP. .IP "\-\-upload\-flags <flags>" (IMAP) Specify additional behavior to apply to uploaded files. Flags are specified as either a single flag value or a comma\-separated list of flag values. These values are case\-sensitive and may be negated by prepending them with a \(aq\-\(aq character. Currently the following flag values are accepted: answered, deleted, draft, flagged, and seen. The currently accepted flag values are used to set flags on IMAP uploads. If \fI\-\-upload\-flags\fP is provided several times, the last set value is used. Example: .nf curl --upload-flags Flagged,!Seen --upload-file local/dir/file https://example.com .fi Added in 8.13.0. See also \fI\-\-upload\-file\fP. .IP "\-\-url <url/file>" Specify a URL to fetch or send data to. If the given URL is missing a scheme (such as "http://" or "ftp://" etc) curl guesses which scheme to use based on the hostname. If the outermost subdomain name matches DICT, FTP, IMAP, LDAP, POP3 or SMTP case insensitively, then that protocol is used, otherwise it assumes HTTP. Scheme guessing can be avoided by providing a full URL including the scheme, or disabled by setting a default protocol, see \fI\-\-proto\-default\fP for details. To control where the contents of a retrieved URL is written instead of the default stdout, use the \fI\-\-output\fP or the \fI\-\-remote\-name\fP options. When retrieving multiple URLs in a single invoke, each provided URL needs its own dedicated destination option unless \fI\-\-remote\-name\-all\fP is used. On Windows, "file://" accesses can be converted to network accesses by the operating system. Starting in curl 8.13.0, curl can be told to download URLs provided in a text file, one URL per line. It is done with "\fI\-\-url\fP @filename": so instead of a URL, you specify a filename prefixed with the "@" symbol. It can be told to load the list of URLs from stdin by providing an argument like "@\-". When downloading URLs given in a file, it implies using \fI\-\-remote\-name\fP for each provided URL. The URLs are full, there is no globbing applied or done on these. Features such as \fI\-\-skip\-existing\fP work fine in combination with this. Lines in the URL file that start with "#" are treated as comments and are skipped. \fI\-\-url\fP can be used several times in a command line. Examples: .nf curl --url https://example.com curl --url @file .fi See also \fI\-\-next\fP, \fI\-\-config\fP, \fI\-\-path\-as\-is\fP and \fI\-\-disallow\-username\-in\-url\fP. .IP "\-\-url\-query <data>" Add a piece of data, usually a name + value pair, to the end of the URL query part. The syntax is identical to that used for \fI\-\-data\-urlencode\fP with one extension: If the argument starts with a \(aq+\(aq (plus), the rest of the string is provided as\-is unencoded. The query part of a URL is the one following the question mark on the right end. \fI\-\-url\-query\fP can be used several times in a command line. Examples: .nf curl --url-query name=val https://example.com curl --url-query =encodethis http://example.net/foo curl --url-query name@file https://example.com curl --url-query @fileonly https://example.com curl --url-query "+name=%20foo" https://example.com .fi Added in 7.87.0. See also \fI\-\-data\-urlencode\fP and \fI\-\-get\fP. .IP "\-B, \-\-use\-ascii" (FTP LDAP TFTP) Enable ASCII transfer mode. For FTP, this can also be enforced by using a URL that ends with ";type=A". For TFTP, this can also be enforced by using a URL that ends with ";mode=netascii". This option causes data sent to stdout to be in text mode for Win32 systems. Providing \fI\-\-use\-ascii\fP multiple times has no extra effect. Disable it again with \-\-no-use-ascii. Example: .nf curl -B ftp://example.com/README .fi See also \fI\-\-crlf\fP and \fI\-\-data\-ascii\fP. .IP "\-u, \-\-user <user:password>" Specify the username and password to use for server authentication. Overrides \fI\-\-netrc\fP and \fI\-\-netrc\-optional\fP. If you specify only the username, curl prompts for a password. The username and passwords are split up on the first colon, which makes it impossible to use a colon in the username with this option. The password can, still. On systems where it works, curl hides the given option argument from process listings. This is not enough to protect credentials from possibly getting seen by other users on the same system as they still are visible for a moment before being cleared. Such sensitive data should be retrieved from a file instead or similar and never used in clear text in a command line. When using Kerberos V5 with a Windows based server you should include the Windows domain name in the username, in order for the server to successfully obtain a Kerberos Ticket. If you do not, then the initial authentication handshake may fail. When using NTLM, the username can be specified without the domain, if there is a single domain and forest in your setup for example. To specify the domain name use either Down\-Level Logon Name or UPN (User Principal Name) formats. For example, EXAMPLE\\user and user@example.com respectively. If you use a Windows SSPI\-enabled curl binary and perform Kerberos V5, Negotiate, NTLM or Digest authentication then you can tell curl to select the username and password from your environment by specifying a single colon with this option: "\-u :". If \fI\-\-user\fP is provided several times, the last set value is used. Example: .nf curl -u user:secret https://example.com .fi See also \fI\-\-netrc\fP and \fI\-\-config\fP. .IP "\-A, \-\-user\-agent <name>" (HTTP) Specify the User\-Agent string to send to the HTTP server. To encode blanks in the string, surround the string with single or double quote marks. This header can also be set with the \fI\-\-header\fP or the \fI\-\-proxy\-header\fP options. If you give an empty argument to \fI\-\-user\-agent\fP (""), it removes the header completely from the request. If you prefer a blank header, you can set it to a single space (" "). By default, curl uses curl/VERSION, such as User\-Agent: curl/8.21.0. If \fI\-\-user\-agent\fP is provided several times, the last set value is used. Example: .nf curl -A "Agent 007" https://example.com .fi See also \fI\-\-header\fP and \fI\-\-proxy\-header\fP. .IP "\-\-variable <[%]name=text/@file>" Set a variable with "name=content" or "name@file" (where "file" can be stdin if set to a single dash ("\-")). The name is a case sensitive identifier that must consist of no other letters than a\-z, A\-Z, 0\-9 or underscore. The specified content is then associated with this identifier. Setting the same variable name again overwrites the old contents with the new. The contents of a variable can be referenced in a later command line option when that option name is prefixed with "\fI\-\-expand\-\fP", and the name is used as \&"{{name}}". \fI\-\-variable\fP can import environment variables into the name space. Opt to either require the environment variable to be set or provide a default value for the variable in case it is not already set. \fI\-\-variable\fP %name imports the variable called "name" but exits with an error if that environment variable is not already set. To provide a default value if the environment variable is not set, use \fI\-\-variable\fP %name=content or \fI\-\-variable\fP %name@content. Note that on some systems \- but not all \- environment variables are case insensitive. Added in curl 8.12.0: you can get a byte range from the source by appending \&"[start\-end]" to the variable name, where \fIstart\fP and \fIend\fP are byte offsets to include from the contents. For example, asking for offset "2\-10" means offset two to offset ten, inclusive, resulting in 9 bytes in total. "2\-2" means a single byte at offset 2. Not providing a second number implies to the end of data. The start offset cannot be larger than the end offset. Asking for a range that is outside of the file size makes the variable contents empty. For example, getting the first one hundred bytes from a given file: .nf curl \--variable "fraction[0\-99]@filename" .fi Given a byte range that has no data results in an empty string. Asking for a range that is larger than the content makes curl use the piece of the data that exists. To assign a variable using contents from another variable, use \fI\-\-expand\-variable\fP. Like for example assigning a new variable using contents from two other: .nf curl \--expand\-variable "user={{firstname}} {{lastname}}" .fi When expanding variables, curl supports a set of functions that can make the variable contents more convenient to use. You apply a function to a variable expansion by adding a colon and then list the desired functions in a comma\-separated list that is evaluated in a left\-to\-right order. Variable content holding null bytes that are not encoded when expanded causes an error. Available functions: .RS .IP trim removes all leading and trailing white space. Example: .nf curl \--expand\-url https://example.com/{{var:trim}} .fi .IP json outputs the content using JSON string quoting rules. Example: .nf curl \--expand\-data {{data:json}} https://example.com .fi .IP url shows the content URL (percent) encoded. Example: .nf curl \--expand\-url https://example.com/{{path:url}} .fi .IP b64 expands the variable base64 encoded Example: .nf curl \--expand\-url https://example.com/{{var:b64}} .fi .IP 64dec decodes a base64 encoded character sequence. If the sequence is not possible to decode, it instead outputs "[64dec\-fail]" Example: .nf curl \--expand\-url https://example.com/{{var:64dec}} .fi (Added in 8.13.0) .RE .IP \fI\-\-variable\fP can be used several times in a command line. Example: .nf curl --variable name=smith --expand-url "https://example.com/{{name}}" .fi Added in 8.3.0. See also \fI\-\-config\fP. .IP "\-v, \-\-verbose" Make curl output verbose information during the operation. Useful for debugging and seeing what\(aqs going on under the hood. Verbose output lines are prefixed with letters: .RS .IP > header sent by curl .IP < header received by curl .IP } data sent by curl .IP { data received by curl .IP * additional info provided by curl. Text that adds explanations what goes on and about choices curl does. .RE .IP If you only want HTTP headers in the output, \fI\-\-show\-headers\fP or \fI\-\-dump\-header\fP might be more suitable options. Since curl 8.10, mentioning this option several times in the same argument increases the level of the trace output. As before, a single \fI\-\-verbose\fP or \fI\-\-no\-verbose\fP reverts any additions by previous "\-vv" again. This means that \&"\-vv \-v" is equivalent to a single \-v. This avoids unwanted verbosity when the option is mentioned in the command line \fIand\fP curl config files. Using it twice, e.g. "\-vv", outputs time (\fI\-\-trace\-time\fP) and transfer ids (\fI\-\-trace\-ids\fP), as well as enabling tracing for all protocols (\fI\-\-trace\-config\fP protocol). Adding a third verbose outputs transfer content (\fI\-\-trace\-ascii\fP %) and enables tracing of more components (\fI\-\-trace\-config\fP read,write,ssl). A fourth time adds tracing of all network components. (\fI\-\-trace\-config\fP network). Any addition of the verbose option after that has no effect. If you think this option does not give you the right details, consider using \fI\-\-trace\fP or \fI\-\-trace\-ascii\fP instead. Or use it only once and use \fI\-\-trace\-config\fP to trace the specific components you wish to see. Note that verbose output of curl activities and network traffic might contain sensitive data, including usernames, credentials or secret data content. Be aware and be careful when sharing trace logs with others. When the output contains protocol headers, those lines might include carriage return (ASCII code 13) characters, even on platforms that otherwise normally only use linefeed to signify line separations \- as curl shows the exact contents arriving from the server. This option is global and does not need to be specified for each use of \fI\-\-next\fP. Providing \fI\-\-verbose\fP multiple times has no extra effect. Disable it again with \-\-no-verbose. Example: .nf curl --verbose https://example.com .fi This option is mutually exclusive with \fI\-\-trace\fP and \fI\-\-trace\-ascii\fP. See also \fI\-\-show\-headers\fP, \fI\-\-silent\fP, \fI\-\-trace\fP and \fI\-\-trace\-ascii\fP. .IP "\-V, \-\-version" Display information about curl and the libcurl version it uses. The first line includes the full version of curl, libcurl and other 3rd party libraries linked with the executable. This line may contain one or more TLS libraries. curl can be built to support more than one TLS library which then makes curl \- at start\-up \- select which particular backend to use for this invocation. If curl supports more than one TLS library like this, the ones that are \fInot\fP selected by default are listed within parentheses. Thus, if you do not specify which backend to use (with the "CURL_SSL_BACKEND" environment variable) the one listed without parentheses is used. Such builds also have "MultiSSL" set as a feature. The second line (starts with "Release\-Date:") shows the release date. The third line (starts with "Protocols:") shows all protocols that libcurl reports to support. The fourth line (starts with "Features:") shows specific features libcurl reports to offer. Available features include: .RS .IP alt-svc Support for the Alt\-Svc: header is provided. .IP AsynchDNS This curl uses asynchronous name resolves. Asynchronous name resolves can be done using either the c\-ares or the threaded resolver backends. .IP brotli Support for automatic brotli compression over HTTP(S). .IP CharConv curl was built with support for character set conversions (like EBCDIC) .IP Debug This curl uses a libcurl built with Debug. This enables more error\-tracking and memory debugging etc. For curl\-developers only. .IP ECH ECH support is present. .IP gsasl The built\-in SASL authentication includes extensions to support SCRAM because libcurl was built with libgsasl. .IP GSS-API GSS\-API is supported. .IP HSTS HSTS support is present. .IP HTTP2 HTTP/2 support has been built\-in. .IP HTTP3 HTTP/3 support has been built\-in. .IP HTTPS-proxy This curl is built to support HTTPS proxy. .IP IDN This curl supports IDN \- international domain names. .IP IPv6 You can use IPv6 with this. .IP Kerberos Kerberos V5 authentication is supported. .IP Largefile This curl supports transfers of large files, files larger than 2GB. .IP libz Automatic decompression (via gzip, deflate) of compressed files over HTTP is supported. .IP MultiSSL This curl supports multiple TLS backends. .IP NTLM NTLM authentication is supported. .IP NTLM_WB NTLM delegation to winbind helper is supported. This feature was removed from curl in 8.8.0. .IP PSL PSL is short for Public Suffix List and means that this curl has been built with knowledge about "public suffixes". .IP SPNEGO SPNEGO authentication is supported. .IP SSL SSL versions of various protocols are supported, such as HTTPS, FTPS, POP3S and so on. .IP SSLS-EXPORT This build supports TLS session export/import, like with the \fI\-\-ssl\-sessions\fP. .IP SSPI SSPI is supported. .IP TLS-SRP SRP (Secure Remote Password) authentication is supported for TLS. .IP Unicode Unicode support on Windows. .IP UnixSockets Unix sockets support is provided. .IP zstd Automatic decompression (via zstd) of compressed files over HTTP is supported. .RE .IP Example: .nf curl --version .fi See also \fI\-\-help\fP and \fI\-\-manual\fP. .IP "\-\-vlan\-priority <priority>" Set VLAN priority as defined in IEEE 802.1Q. This field is set on Ethernet level, and only works within a local network. The valid range for <priority> is 0 to 7. If \fI\-\-vlan\-priority\fP is provided several times, the last set value is used. Example: .nf curl --vlan-priority 4 https://example.com .fi Added in 8.9.0. See also \fI\-\-ip\-tos\fP. .IP "\-w, \-\-write\-out <format>" Make curl display information on stdout after a completed transfer. The format is a string that may contain plain text mixed with any number of variables. The format can be specified as a literal "string", or you can have curl read the format from a file with "@filename" and to tell curl to read the format from stdin you write "@\-". The variables present in the output format are substituted by the value or text that curl thinks fit, as described below. All variables are specified as %{variable_name} and to output a normal % you write them as %%. You can output a newline by using \\n, a carriage return with \\r and a tab space with \\t. The output is by default written to standard output, but can be changed with %{stderr} and %output{}. Output HTTP header values from the transfer\(aqs most recent server response by using \fI%header{name}\fP where \fIname\fP is the case insensitive name of the header (without the trailing colon). The header contents are exactly as delivered over the network but with leading and trailing whitespace and newlines stripped off (added in 7.84.0). Select a specific target destination file to write the output to, by using \fI%output{name}\fP (added in curl 8.3.0) where \fIname\fP is the full filename. The output following that instruction is then written to that file. More than one \fI%output{}\fP instruction can be specified in the same write\-out argument. If the filename cannot be created, curl leaves the output destination to the one used prior to the \fI%output{}\fP instruction. Use \fI%output{>>name}\fP to append data to an existing file. This output is done independently of if the file transfer was successful or not. If the specified action or output specified with this option fails in any way, it does not make curl return a (different) error. \fBNOTE:\fP On Windows, the %\-symbol is a special symbol used to expand environment variables. In batch files, all occurrences of % must be doubled when using this option to properly escape. If this option is used at the command prompt then the % cannot be escaped and unintended expansion is possible. The variables available are: .RS .IP certs Output the certificate chain with details. Supported only by the OpenSSL, GnuTLS, Schannel and Rustls backends. (Added in 7.88.0) .IP conn_id The connection identifier last used by the transfer. The connection id is unique number among all connections using the same connection cache. (Added in 8.2.0) .IP content_type The Content\-Type of the requested document, if there was any. .IP errormsg The error message. (Added in 7.75.0) .IP exitcode The numerical exit code of the transfer. (Added in 7.75.0) .IP filename_effective The ultimate filename that curl writes out to. This is only meaningful if curl is told to write to a file with the \fI\-\-remote\-name\fP or \fI\-\-output\fP option. It is most useful in combination with the \fI\-\-remote\-header\-name\fP option. .IP ftp_entry_path The initial path curl ended up in when logging on to the remote FTP server. .IP header{name} The value of header "name" from the transfer\(aqs most recent server response. Unlike other variables, the variable name "header" is not in braces. For example "%header{date}". Refer to \fI\-\-write\-out\fP remarks. (Added in 7.84.0) Starting with 8.17.0, output the contents of \fIall\fP header fields using a specific name \- even for a whole redirect "chain" by appending \&":all:[separator]" to the header name. The "[separator]" string (if not blank) is output between the headers if there are more than one. When more than one header is shown, they are output in the chronological order of appearance over the wire. To include a close brace ("}") in the separator, escape it with a backslash: "\\}". .IP header_json A JSON object with all HTTP response headers from the recent transfer. Values are provided as arrays, since in the case of multiple headers there can be multiple values. (Added in 7.83.0) The header names provided in lowercase, listed in order of appearance over the wire. Except for duplicated headers. They are grouped on the first occurrence of that header, each value is presented in the JSON array. .IP http_code The numerical response code that was found in the last retrieved HTTP(S) or FTP(s) transfer. .IP http_connect The numerical code that was found in the last response (from a proxy) to a curl CONNECT request. .IP http_version The http version that was effectively used. .IP json A JSON object with all available keys except "header_json". (Added in 7.70.0) .IP local_ip The IP address of the local end of the most recently done connection \- can be either IPv4 or IPv6. .IP local_port The local port number of the most recently done connection. .IP method The http method used in the most recent HTTP request. (Added in 7.72.0) .IP num_certs Number of server certificates received in the TLS handshake. Supported only by the OpenSSL, GnuTLS, Schannel and Rustls backends. (Added in 7.88.0) .IP num_connects Number of new connects made in the recent transfer. .IP num_headers The number of response headers in the most recent request (restarted at each redirect). Note that the status line IS NOT a header. (Added in 7.73.0) .IP num_redirects Number of redirects that were followed in the request. .IP num_retries Number of retries actually performed when "\fI\-\-retry\fP" has been used. (Added in 8.9.0) .IP onerror The rest of the output is only shown if the transfer returned a non\-zero error. (Added in 7.75.0) .IP output{filename} From this point on, the \fI\-\-write\-out\fP output is written to the filename specified in braces. The filename can be prefixed with ">>" to append to the file. Unlike other variables, the variable name "output" is not in braces. For example \&"%output{>>stats.txt}". Refer to \fI\-\-write\-out\fP remarks. (Added in 8.3.0) .IP proxy_ssl_verify_result The result of the HTTPS proxy\(aqs SSL peer certificate verification that was requested. 0 means the verification was successful. .IP proxy_used Returns 1 if the previous transfer used a proxy, otherwise 0. Useful for example to determine if a "NOPROXY" pattern matched the hostname or not. (Added in 8.7.0) .IP redirect_url When an HTTP request was made without \fI\-\-location\fP to follow redirects (or when \fI\-\-max\-redirs\fP is met), this variable shows the actual URL a redirect \fIwould\fP have gone to. .IP referer The Referer: header, if there was any. (Added in 7.76.0) .IP remote_ip The remote IP address of the most recently done connection \- can be either IPv4 or IPv6. .IP remote_port The remote port number of the most recently done connection. .IP response_code The numerical response code that was found in the last transfer (formerly known as "http_code"). .IP scheme The URL scheme (sometimes called protocol) that was effectively used. .IP size_delivered The total amount of data that were saved or written to stdout. When \fI\-\-compressed\fP is used, this is likely different than "size_download". Includes the headers in the count if \fI\-\-include\fP is used. .IP size_download The total amount of bytes that were downloaded. This is the size of the body/data that was transferred, excluding headers. .IP size_header The total amount of bytes of the downloaded headers, as represented in HTTP/1\-style header format. .IP size_request The total amount of bytes that were sent in the HTTP request. .IP size_upload The total amount of bytes that were uploaded. This is the size of the body/data that was transferred, excluding headers. .IP speed_download The average download speed that curl measured for the complete download. Bytes per second. .IP speed_upload The average upload speed that curl measured for the complete upload. Bytes per second. .IP ssl_verify_result The result of the SSL peer certificate verification that was requested. 0 means the verification was successful. .IP stderr From this point on, the \fI\-\-write\-out\fP output is written to standard error. .IP stdout From this point on, the \fI\-\-write\-out\fP output is written to standard output. This is the default, but can be used to switch back after switching to stderr. .IP time{format} Output the current UTC time using "strftime()" format. See TIME OUTPUT FORMAT below for details. (Added in 8.16.0) .IP time_appconnect The time, in seconds, it took from the start until the SSL/SSH/etc connect/handshake to the remote host was completed. .IP time_connect The time, in seconds, it took from the start until the TCP connect to the remote host (or proxy) was completed. .IP time_namelookup The time, in seconds, it took from the start until the name resolving was completed. .IP time_posttransfer The time, in seconds, it took from the start until the last byte is sent by libcurl. (Added in 8.10.0) .IP time_pretransfer The time, in seconds, it took from the start until immediately before the file transfer was about to begin. This includes all pre\-transfer commands and negotiations that are specific to the particular protocol(s) involved. .IP time_queue The time, in seconds, the transfer was queued during its run. This adds the queue time for each redirect step that may have happened. Transfers may be queued for significant amounts of time when connection or parallel limits are in place. (Added in 8.12.0) .IP time_redirect The time, in seconds, it took for all redirection steps including name lookup, connect, pretransfer and transfer before the final transaction was started. "time_redirect" shows the complete execution time for multiple redirections. .IP time_starttransfer The time, in seconds, it took from the start until the first byte was received. This includes time_pretransfer and also the time the server needed to calculate the result. .IP time_total The total time, in seconds, that the full operation lasted. .IP tls_earlydata The amount of bytes that were sent as TLSv1.3 early data. This is 0 if this TLS feature was not used and negative if the data sent had been rejected by the server. The use of early data is enabled via the command line option "\fI\-\-tls\-earlydata\fP". (Added in 8.13.0) .IP url The URL that was fetched. (Added in 7.75.0) .IP url.scheme The scheme part of the URL that was fetched. (Added in 8.1.0) .IP url.user The user part of the URL that was fetched. (Added in 8.1.0) .IP url.password The password part of the URL that was fetched. (Added in 8.1.0) .IP url.options The options part of the URL that was fetched. (Added in 8.1.0) .IP url.host The host part of the URL that was fetched. (Added in 8.1.0) .IP url.port The port number of the URL that was fetched. If no port number was specified and the URL scheme is known, that scheme\(aqs default port number is shown. (Added in 8.1.0) .IP url.path The path part of the URL that was fetched. (Added in 8.1.0) .IP url.query The query part of the URL that was fetched. (Added in 8.1.0) .IP url.fragment The fragment part of the URL that was fetched. (Added in 8.1.0) .IP url.zoneid The zone id part of the URL that was fetched. (Added in 8.1.0) .IP urle.scheme The scheme part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urle.user The user part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urle.password The password part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urle.options The options part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urle.host The host part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urle.port The port number of the effective (last) URL that was fetched. If no port number was specified, but the URL scheme is known, that scheme\(aqs default port number is shown. (Added in 8.1.0) .IP urle.path The path part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urle.query The query part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urle.fragment The fragment part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urle.zoneid The zone id part of the effective (last) URL that was fetched. (Added in 8.1.0) .IP urlnum The URL index number of this transfer, 0\-indexed. Unglobbed URLs share the same index number as the origin globbed URL. (Added in 7.75.0) .IP url_effective The URL that was fetched last. This is most meaningful if you have told curl to follow location: headers. .IP xfer_id The numerical identifier of the last transfer done. \-1 if no transfer has been started yet for the handle. The transfer id is unique among all transfers performed using the same connection cache. (Added in 8.2.0) .RE .IP TIME OUTPUT FORMAT To show time with "%time{}" the characters within "{}" create a special format string that may contain special character sequences called conversion specifications. Each conversion specification starts with "%" and is followed by a character that instructs curl to output a particular time detail. All other characters used are displayed as\-is. The following conversion specification are available: .RS .IP %a The abbreviated name of the day of the week according to the current locale. .IP %A The full name of the day of the week according to the current locale. .IP %b The abbreviated month name according to the current locale. .IP %B The full month name according to the current locale. .IP %c The preferred date and time representation for the current locale. (In the POSIX locale this is equivalent to "%a %b %e %H:%M:%S %Y".) .IP %C The century number (year/100) as a 2\-digit integer. .IP %d The day of the month as a decimal number (range 01 to 31). .IP %D Equivalent to "%m/%d/%y". In international contexts, this format is ambiguous and should be avoided.) .IP %e Like "%d", the day of the month as a decimal number, but a leading zero is replaced by a space. .IP %f The number of microseconds elapsed of the current second. (This a curl special code and not a standard one.) .IP %F Equivalent to "%Y\-%m\-%d" (the ISO 8601 date format). .IP %G The ISO 8601 week\-based year with century as a decimal number. The 4\-digit year corresponding to the ISO week number (see "%V"). This has the same format and value as "%Y", except that if the ISO week number belongs to the previous or next year, that year is used instead. .IP %g Like "%G", but without century, that is, with a 2\-digit year (00\-99). .IP %h Equivalent to "%b". .IP %H The hour as a decimal number using a 24\-hour clock (range 00 to 23). .IP %I The hour as a decimal number using a 12\-hour clock (range 01 to 12). .IP %j The day of the year as a decimal number (range 001 to 366). .IP %k The hour (24\-hour clock) as a decimal number (range 0 to 23); single digits are preceded by a blank. .IP %l The hour (12\-hour clock) as a decimal number (range 1 to 12); single digits are preceded by a blank. .IP %m The month as a decimal number (range 01 to 12). .IP %M The minute as a decimal number (range 00 to 59). .IP %p Either "AM" or "PM" according to the given time value, or the corresponding strings for the current locale. Noon is treated as "PM" and midnight as "AM". .IP %P Like "%p" but in lowercase: "am" or "pm" or a corresponding string for the current locale. .IP %r The time in am or pm notation. .IP %R The time in 24\-hour notation ("%H:%M"). For a version including the seconds, see "%T" below. .IP %s The number of seconds since the Epoch, 1970\-01\-01 00:00:00 +0000 (UTC). .IP %S The second as a decimal number (range 00 to 60). (The range is up to 60 to allow for occasional leap seconds.) See "%f" for microseconds. .IP %T The time in 24\-hour notation ("%H:%M:%S"). .IP %u The day of the week as a decimal, range 1 to 7, Monday being 1. .IP %U The week number of the current year as a decimal number, range 00 to 53, starting with the first Sunday as the first day of week 01. See also "%V" and \&"%W". .IP %V The ISO 8601 week number (see NOTES) of the current year as a decimal number, range 01 to 53, where week 1 is the first week that has at least 4 days in the new year. See also "%U" and "%W". .IP %w The day of the week as a decimal, range 0 to 6, Sunday being 0. See also "%u". .IP %W The week number of the current year as a decimal number, range 00 to 53, starting with the first Monday as the first day of week 01. .IP %x The preferred date representation for the current locale without the time. .IP %X The preferred time representation for the current locale without the date. .IP %y The year as a decimal number without a century (range 00 to 99). .IP %Y The year as a decimal number including the century. .IP %z The "+hhmm" or "\-hhmm" numeric timezone (that is, the hour and minute offset from UTC). As time is always UTC, this outputs "+0000". .IP %Z The timezone name. For some reason "GMT". .IP %% A literal "%" character. .RE .IP If \fI\-\-write\-out\fP is provided several times, the last set value is used. Example: .nf curl -w '%{response_code}\\n' https://example.com .fi See also \fI\-\-verbose\fP and \fI\-\-head\fP. .IP "\-\-xattr" Store metadata in the extended file attributes. When saving output to a file, tell curl to store file metadata in extended file attributes. Currently, "curl" is stored in the "creator" attribute, the URL is stored in the "xdg.origin.url" attribute and, for HTTP, the content type is stored in the "mime_type" attribute. If the file system does not support extended attributes, a warning is issued. Providing \fI\-\-xattr\fP multiple times has no extra effect. Disable it again with \-\-no-xattr. Example: .nf curl --xattr -o storage https://example.com .fi See also \fI\-\-remote\-time\fP, \fI\-\-write\-out\fP and \fI\-\-verbose\fP. .SH FILES \fI~/.curlrc\fP Default config file, see \fI\-\-config\fP for details. .SH ENVIRONMENT The environment variables can be specified in lower case or upper case. The lower case version has precedence. "http_proxy" is an exception as it is only available in lower case. (Note that some systems, like Windows, do not differentiate between environment variables using different case.) Using an environment variable to set the proxy has the same effect as using the \fI\-\-proxy\fP option. .IP "http_proxy [protocol://]<host>[:port]" Sets the proxy server to use for HTTP. .IP "HTTPS_PROXY [protocol://]<host>[:port]" Sets the proxy server to use for HTTPS. .IP "[url-protocol]_PROXY [protocol://]<host>[:port]" Sets the proxy server to use for [url\-protocol], where the protocol is a protocol that curl supports and as specified in a URL. FTP, FTPS, POP3, IMAP, SMTP, LDAP, etc. .IP "ALL_PROXY [protocol://]<host>[:port]" Sets the proxy server to use if no protocol\-specific proxy is set. .IP "NO_PROXY <comma-separated list of hosts/domains>" list of hostnames that should not go through any proxy. If set to an asterisk \(aq*\(aq only, it matches all hosts. Each name in this list is matched as either a domain name which contains the hostname, or the hostname itself. This environment variable disables use of the proxy even when specified with the \fI\-\-proxy\fP option. That is .nf NO_PROXY=direct.example.com curl \-x http://proxy.example.com https://direct.example.com .fi accesses the target URL directly, and .nf NO_PROXY=direct.example.com curl \-x http://proxy.example.com https://somewhere.example.com .fi accesses the target URL through the proxy. The list of hostnames can also include numerical IP addresses, and IPv6 versions should then be given without enclosing brackets. IP addresses can be specified using CIDR notation: an appended slash and number specifies the number of "network bits" out of the address to use in the comparison (added in 7.86.0). For example "192.168.0.0/16" would match all addresses starting with "192.168". .IP "APPDATA <directory>" On Windows, this variable is used when trying to find the home directory. If the primary home variables are all unset. .IP "COLUMNS <terminal width>" If set, the specified number of characters is used as the terminal width when the alternative progress\-bar is shown. If not set, curl tries to figure it out using other ways. .IP "CURL_CA_BUNDLE <file>" If set, it is used as the \fI\-\-cacert\fP value. This environment variable is ignored if Schannel is used as the TLS backend. .IP "CURL_HOME <directory>" If set, is the first variable curl checks when trying to find its home directory. If not set, it continues to check \fIXDG_CONFIG_HOME\fP .IP "CURL_SSL_BACKEND <TLS backend>" If curl was built with support for "MultiSSL", meaning that it has built\-in support for more than one TLS backend, this environment variable can be set to the case insensitive name of the particular backend to use when curl is invoked. Setting a name that is not a built\-in alternative makes curl stay with the default. SSL backend names (case\-insensitive): \fBgnutls\fP, \fBmbedtls\fP, \fBopenssl\fP, \fBrustls\fP, \fBschannel\fP, \fBwolfssl\fP .IP "HOME <directory>" If set, this is used to find the home directory when that is needed. Like when looking for the default .curlrc. \fICURL_HOME\fP and \fIXDG_CONFIG_HOME\fP have preference. .IP "NETRC <path>" If set, this is used to find the ".netrc" file. It overrides all other netrc file location mechanisms and should be set to the full file path. (Added in curl 8.16.0) .IP "QLOGDIR <directory>" If curl was built with HTTP/3 support, setting this environment variable to a local directory makes curl produce \fBqlogs\fP in that directory, using file names named after the destination connection id (in hex). Do note that these files can become rather large. Works with the ngtcp2 and quiche QUIC backends. .IP SHELL Used on VMS when trying to detect if using a \fBDCL\fP or a \fBUnix\fP shell. .IP "SSL_CERT_DIR <directory>" If set, it is used as the \fI\-\-capath\fP value. This environment variable is ignored if Schannel is used as the TLS backend. .IP "SSL_CERT_FILE <path>" If set, it is used as the \fI\-\-cacert\fP value. This environment variable is ignored if Schannel is used as the TLS backend. .IP "SSLKEYLOGFILE <path>" If you set this environment variable to a filename, curl stores TLS secrets from its connections in that file when invoked to enable you to analyze the TLS traffic in real time using network analyzing tools such as Wireshark. This works with the following TLS backends: OpenSSL, LibreSSL (TLS 1.2 max), BoringSSL, GnuTLS, wolfSSL and Rustls. .IP "USERPROFILE <directory>" On Windows, this variable is used when trying to find the home directory. If the other, primary, variables are all unset. If set, curl uses the path \fB"$USERPROFILE\\Application Data"\fP. .IP "XDG_CONFIG_HOME <directory>" If \fICURL_HOME\fP is not set, this variable is checked when looking for a default .curlrc file. .SH PROXY PROTOCOL PREFIXES The proxy string may be specified with a "protocol://" prefix to specify alternative proxy protocols. If no protocol is specified in the proxy string or if the string does not match a supported one, the proxy is treated as an HTTP proxy. The supported proxy protocol prefixes are as follows: .IP http:// Makes it use it as an HTTP proxy. The default if no scheme prefix is used. .IP https:// Makes it treated as an \fBHTTPS\fP proxy. .IP socks4:// Makes it the equivalent of \fI\-\-socks4\fP .IP socks4a:// Makes it the equivalent of \fI\-\-socks4a\fP .IP socks5:// Makes it the equivalent of \fI\-\-socks5\fP .IP socks5h:// Makes it the equivalent of \fI\-\-socks5\-hostname\fP .SH EXIT CODES There are a bunch of different error codes and their corresponding error messages that may appear under error conditions. At the time of this writing, the exit codes are: .IP 0 Success. The operation completed successfully according to the instructions. .IP 1 Unsupported protocol. This build of curl has no support for this protocol. .IP 2 Failed to initialize. .IP 3 URL malformed. The syntax was not correct. .IP 4 A feature or option that was needed to perform the desired request was not enabled or was explicitly disabled at build\-time. To make curl able to do this, you probably need another build of libcurl. .IP 5 Could not resolve proxy. The given proxy host could not be resolved. .IP 6 Could not resolve host. The given remote host could not be resolved. .IP 7 Failed to connect to host. .IP 8 Weird server reply. The server sent data curl could not parse. .IP 9 FTP access denied. The server denied login or denied access to the particular resource or directory you wanted to reach. Most often you tried to change to a directory that does not exist on the server. .IP 10 FTP accept failed. While waiting for the server to connect back when an active FTP session is used, an error code was sent over the control connection or similar. .IP 11 FTP weird PASS reply. curl could not parse the reply sent to the PASS request. .IP 12 During an active FTP session while waiting for the server to connect back to curl, the timeout expired. .IP 13 FTP weird PASV reply, curl could not parse the reply sent to the PASV request. .IP 14 FTP weird 227 format. curl could not parse the 227\-line the server sent. .IP 15 FTP cannot use host. Could not resolve the host IP we got in the 227\-line. .IP 16 HTTP/2 error. A problem was detected in the HTTP2 framing layer. This is somewhat generic and can be one out of several problems, see the error message for details. .IP 17 FTP could not set binary. Could not change transfer method to binary. .IP 18 Partial file. Only a part of the file was transferred. .IP 19 FTP could not download/access the given file, the RETR (or similar) command failed. .IP 21 FTP quote error. A quote command returned error from the server. .IP 22 HTTP page not retrieved. The requested URL was not found or returned another error with the HTTP error code being 400 or above. This return code only appears if \fI\-\-fail\fP is used. .IP 23 Write error. curl could not write data to a local file system or similar. .IP 25 Failed starting the upload. For FTP, the server typically denied the STOR command. .IP 26 Read error. Various reading problems. .IP 27 Out of memory. A memory allocation request failed. .IP 28 Operation timeout. The specified time\-out period was reached according to the conditions. .IP 30 FTP PORT failed. The PORT command failed. Not all FTP servers support the PORT command, try doing a transfer using PASV instead. .IP 31 FTP could not use REST. The REST command failed. This command is used for resumed FTP transfers. .IP 33 HTTP range error. The range "command" did not work. .IP 34 HTTP post error. Internal post\-request generation error. .IP 35 SSL connect error. The SSL handshaking failed. .IP 36 Bad download resume. Could not continue an earlier aborted download. .IP 37 FILE could not read file. Failed to open the file. Permissions? .IP 38 LDAP cannot bind. LDAP bind operation failed. .IP 39 LDAP search failed. .IP 41 Function not found. A required LDAP function was not found. .IP 42 Aborted by callback. An application told curl to abort the operation. .IP 43 Internal error. A function was called with a bad parameter. .IP 45 Interface error. A specified outgoing interface could not be used. .IP 47 Too many redirects. When following redirects, curl hit the maximum amount. .IP 48 Unknown option specified to libcurl. This indicates that you passed a weird option to curl that was passed on to libcurl and rejected. Read up in the manual. .IP 49 Malformed telnet option. .IP 52 The server did not reply anything, which here is considered an error. .IP 53 SSL crypto engine not found. .IP 54 Cannot set SSL crypto engine as default. .IP 55 Failed sending network data. .IP 56 Failure in receiving network data. .IP 58 Problem with the local certificate. .IP 59 Could not use specified SSL cipher. .IP 60 Peer certificate cannot be authenticated with known CA certificates. .IP 61 Unrecognized transfer encoding. .IP 63 Maximum file size exceeded. .IP 64 Requested FTP SSL level failed. .IP 65 Sending the data requires a rewind that failed. .IP 66 Failed to initialize SSL Engine. .IP 67 The username, password, or similar was not accepted and curl failed to log in. .IP 68 File not found on TFTP server. .IP 69 Permission problem on TFTP server. .IP 70 Out of disk space on TFTP server. .IP 71 Illegal TFTP operation. .IP 72 Unknown TFTP transfer ID. .IP 73 File already exists (TFTP). .IP 74 No such user (TFTP). .IP 77 Problem reading the SSL CA cert (path? access rights?). .IP 78 The resource referenced in the URL does not exist. .IP 79 An unspecified error occurred during the SSH session. .IP 80 Failed to shut down the SSL connection. .IP 82 Could not load CRL file, missing or wrong format. .IP 83 Issuer check failed. .IP 84 The FTP PRET command failed. .IP 85 Mismatch of RTSP CSeq numbers. .IP 86 Mismatch of RTSP Session Identifiers. .IP 87 Unable to parse FTP file list. .IP 88 FTP chunk callback reported error. .IP 89 No connection available, the session is queued. .IP 90 SSL public key does not match pinned public key. .IP 91 Invalid SSL certificate status. .IP 92 Stream error in HTTP/2 framing layer. .IP 93 An API function was called from inside a callback. .IP 94 An authentication function returned an error. .IP 95 A problem was detected in the HTTP/3 layer. This is somewhat generic and can be one out of several problems, see the error message for details. .IP 96 QUIC connection error. This error may be caused by an SSL library error. QUIC is the protocol used for HTTP/3 transfers. .IP 97 Proxy handshake error. .IP 98 A client\-side certificate is required to complete the TLS handshake. .IP 99 Poll or select returned fatal error. .IP 100 A value or data field grew larger than allowed. .IP XX More error codes might appear here in future releases. The existing ones are meant to never change. .SH BUGS If you experience any problems with curl, submit an issue in the project\(aqs bug tracker on GitHub: https://github.com/curl/curl/issues .SH AUTHORS Daniel Stenberg is the main author, but the whole list of contributors is found in the separate THANKS file. .SH WWW https://curl.se/ .SH SEE ALSO \fBftp(1)\fP, \fBwget(1)\fP usr/bin/wcurl 0000755 00000026475 15233257621 0007233 0 ustar 00 #!/bin/sh # wcurl - a simple wrapper around curl to easily download files. # # Requires curl >= 7.46.0 (2015) # # Copyright (C) Samuel Henrique <samueloph@debian.org>, Sergio Durigan # Junior <sergiodj@debian.org> and many contributors, see the AUTHORS # file. # # Permission to use, copy, modify, and distribute this software for any purpose # with or without fee is hereby granted, provided that the above copyright # notice and this permission notice appear in all copies. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. IN # NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, # DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR # OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE # OR OTHER DEALINGS IN THE SOFTWARE. # # Except as contained in this notice, the name of a copyright holder shall not be # used in advertising or otherwise to promote the sale, use or other dealings in # this Software without prior written authorization of the copyright holder. # # SPDX-License-Identifier: curl # Stop on errors and on usage of unset variables. set -eu VERSION="2026.01.05" PROGRAM_NAME="$(basename "$0")" readonly PROGRAM_NAME # Display the version. print_version() { cat << _EOF_ ${VERSION} _EOF_ } # Display the program usage. usage() { cat << _EOF_ ${PROGRAM_NAME} -- a simple wrapper around curl to easily download files. Usage: ${PROGRAM_NAME} <URL>... ${PROGRAM_NAME} [--curl-options <CURL_OPTIONS>]... [--no-decode-filename] [-o|-O|--output <PATH>] [--dry-run] [--] <URL>... ${PROGRAM_NAME} [--curl-options=<CURL_OPTIONS>]... [--no-decode-filename] [--output=<PATH>] [--dry-run] [--] <URL>... ${PROGRAM_NAME} -h|--help ${PROGRAM_NAME} -V|--version Options: --curl-options <CURL_OPTIONS>: Specify extra options to be passed when invoking curl. May be specified more than once. -o, -O, --output <PATH>: Use the provided output path instead of getting it from the URL. If multiple URLs are provided, resulting files share the same name with a number appended to the end (curl >= 7.83.0). If this option is provided multiple times, only the last value is considered. --no-decode-filename: Do not percent-decode the output filename, even if the percent-encoding in the URL was done by wcurl, e.g.: The URL contained whitespace. --dry-run: Do not actually execute curl, only print what would be invoked. -V, --version: Print version information. -h, --help: Print this usage message. <CURL_OPTIONS>: Any option supported by curl can be set here. This is not used by wcurl; it is instead forwarded to the curl invocation. <URL>: URL to be downloaded. Anything that is not a parameter is considered an URL. Whitespace is percent-encoded and the URL is passed to curl, which then performs the parsing. May be specified more than once. _EOF_ } # Display an error message and bail out. error() { printf "%s\n" "$*" >&2 exit 1 } # Extra curl options provided by the user. # This is set per-URL for every URL provided. # Some options are global, but we are erroring on the side of needlessly setting # them multiple times instead of causing issues with parameters that needs to # be set per-URL. CURL_OPTIONS="" # The URLs to be downloaded. URLS="" # Variable used to be set to the percent-decoded filename parsed from the URL, unless # --output or --no-decode-filename are used. OUTPUT_PATH="" HAS_USER_SET_OUTPUT="false" # The parameters that are passed per-URL to curl. readonly PER_URL_PARAMETERS="\ --fail \ --globoff \ --location \ --proto-default https \ --remote-time \ --retry 5 " # Valid percent-encode codes that are considered unsafe to be decoded. # This is a list of space-separated percent-encoded uppercase # characters. # 2F = / # 5C = \ # 3A = : readonly UNSAFE_PERCENT_ENCODE="%2F %5C %3A" # Whether to invoke curl or not. DRY_RUN="false" # Sanitize parameters. sanitize() { if [ -z "${URLS}" ]; then error "You must provide at least one URL to download." fi readonly CURL_OPTIONS URLS DRY_RUN HAS_USER_SET_OUTPUT } # Indicate via exit code whether the string given in the first parameter # consists solely of characters from the string given in the second parameter. # In other words, it returns 0 if the first parameter only contains characters # from the second parameter, e.g.: Are $1 characters a subset of $2 characters? is_subset_of() { case "${1}" in *[!${2}]* | '') return 1 ;; esac } # Indicate via exit code whether the HTML code given in the first # parameter is safe to be decoded. is_safe_percent_encode() { upper_str=$(printf "%s" "${1}" | tr "[:lower:]" "[:upper:]") for unsafe in ${UNSAFE_PERCENT_ENCODE}; do if [ "${unsafe}" = "${upper_str}" ]; then return 1 fi done return 0 } # Print the given string percent-decoded. percent_decode() { # Encodings of control characters (00-1F) are passed through without decoding. # Iterate on the input character-by-character, decoding it. printf "%s\n" "${1}" | fold -w1 | while IFS= read -r decode_out; do # If character is a "%", read the next character as decode_hex1. if [ "${decode_out}" = % ] && IFS= read -r decode_hex1; then decode_out="${decode_out}${decode_hex1}" # If there is one more character, read it as decode_hex2. if IFS= read -r decode_hex2; then decode_out="${decode_out}${decode_hex2}" # Skip decoding if this is a control character (00-1F). # Skip decoding if DECODE_FILENAME is not "true". if [ "${DECODE_FILENAME}" = "true" ] \ && is_subset_of "${decode_hex1}" "23456789abcdefABCDEF" \ && is_subset_of "${decode_hex2}" "0123456789abcdefABCDEF" \ && is_safe_percent_encode "${decode_out}"; then # Use printf to decode it into octal and then decode it to the final format. decode_out="$(printf "%b" "\\$(printf %o "0x${decode_hex1}${decode_hex2}")")" fi fi fi printf %s "${decode_out}" done } # Print the percent-decoded filename portion of the given URL. get_url_filename() { # Remove protocol and query string if present. hostname_and_path="$(printf %s "${1}" | sed -e 's,^[^/]*//,,' -e 's,?.*$,,')" # If what remains contains a slash, there is a path; return it percent-decoded. case "${hostname_and_path}" in # sed to remove everything preceding the last '/', e.g.: "example/something" becomes "something" # sed to also replace ':' with the percent_encoded %3A */*) percent_decode "$(printf %s "${hostname_and_path}" | sed -e 's,^.*/,,' -e 's,:,%3A,g')" ;; esac # No slash means there was only a hostname and no path; return empty string. } # Execute curl with the list of URLs provided by the user. exec_curl() { CMD="curl " # Store version to check if it supports --no-clobber, --parallel and --parallel-max-host. curl_version=$($CMD --version | cut -f2 -d' ' | head -n1) curl_version_major=$(echo "$curl_version" | cut -f1 -d.) curl_version_minor=$(echo "$curl_version" | cut -f2 -d.) CURL_NO_CLOBBER="" CURL_PARALLEL="" if [ "${curl_version_major}" -ge 8 ]; then CURL_NO_CLOBBER="--no-clobber" CURL_PARALLEL="--parallel --parallel-max-host 5" # --parallel-max-host is only supported since 8.16.0. if [ "${curl_version_major}" -eq 8 ] && [ "${curl_version_minor}" -lt 16 ]; then CURL_PARALLEL="--parallel" fi elif [ "${curl_version_major}" -eq 7 ]; then # --no-clobber is only supported since 7.83.0. if [ "${curl_version_minor}" -ge 83 ]; then CURL_NO_CLOBBER="--no-clobber" fi # --parallel is only supported since 7.66.0. if [ "${curl_version_minor}" -ge 66 ]; then CURL_PARALLEL="--parallel" fi fi # Detecting whether we need --parallel. It is easier to rely on # the shell's argument parsing. # shellcheck disable=SC2086 set -- $URLS # If there are less than two URLs, do not set the parallel flag. if [ "$#" -lt 2 ]; then CURL_PARALLEL="" fi # Start assembling the command. # # We use 'set --' here (again) because (a) we do not have arrays on # POSIX shell, and (b) we need better control over the way we # split arguments. # # shellcheck disable=SC2086 set -- ${CMD} ${CURL_PARALLEL} NEXT_PARAMETER="" for url in ${URLS}; do # If the user did not provide an output path, define one. if [ "${HAS_USER_SET_OUTPUT}" = "false" ]; then OUTPUT_PATH="$(get_url_filename "${url}")" # If we could not get a path from the URL, use the default: index.html. [ -z "${OUTPUT_PATH}" ] && OUTPUT_PATH=index.html fi # shellcheck disable=SC2086 set -- "$@" ${NEXT_PARAMETER} ${PER_URL_PARAMETERS} ${CURL_NO_CLOBBER} --output "${OUTPUT_PATH}" ${CURL_OPTIONS} "${url}" NEXT_PARAMETER="--next" done if [ "${DRY_RUN}" = "false" ]; then exec "$@" else printf "%s\n" "$@" fi } # Default to decoding the output filename DECODE_FILENAME="true" # Use "${1-}" in order to avoid errors because of 'set -u'. while [ -n "${1-}" ]; do case "${1}" in --curl-options=*) opt=$(printf "%s\n" "${1}" | sed 's/^--curl-options=//') CURL_OPTIONS="${CURL_OPTIONS} ${opt}" ;; --curl-options) shift CURL_OPTIONS="${CURL_OPTIONS} ${1}" ;; --dry-run) DRY_RUN="true" ;; --output=*) opt=$(printf "%s\n" "${1}" | sed 's/^--output=//') HAS_USER_SET_OUTPUT="true" OUTPUT_PATH="${opt}" ;; -o | -O | --output) shift HAS_USER_SET_OUTPUT="true" OUTPUT_PATH="${1}" ;; -o* | -O*) opt=$(printf "%s\n" "${1}" | sed 's/^-[oO]//') HAS_USER_SET_OUTPUT="true" OUTPUT_PATH="${opt}" ;; --no-decode-filename) DECODE_FILENAME="false" ;; -h | --help) usage exit 0 ;; -V | --version) print_version exit 0 ;; --) # This is the start of the list of URLs. shift for url in "$@"; do # Encode whitespace into %20, since wget supports those URLs. newurl=$(printf "%s\n" "${url}" | sed 's/ /%20/g') URLS="${URLS} ${newurl}" done break ;; -*) error "Unknown option: '$1'." ;; *) # This must be a URL. # Encode whitespace into %20, since wget supports those URLs. newurl=$(printf "%s\n" "${1}" | sed 's/ /%20/g') URLS="${URLS} ${newurl}" ;; esac shift done sanitize exec_curl usr/bin/curl 0000755 00002557520 15233257622 0007047 0 ustar 00 ELF >