/home/crealab/cntxt.brainware.com.co/curlssl11.tar
usr/share/man/man1/curl.1 0000644 00000763637 15116230423 0011140 0 ustar 00 .\" **************************************************************************
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" DO NOT EDIT. Generated by the curl project managen manpage generator.
.\"
.TH curl 1 "2025-06-13" "curl 8.14.1" "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, POP3, POP3S, RTMP, RTMPS, 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 find a detailed description in
RFC 3986.
If you provide a URL without a leading \fBprotocol://\fP 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\-Z, \-\-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.
Provide an IPv6 zone id in the URL with an escaped percentage sign. Like in
.nf
\&"http://[fe80::3%25eth0]/"
.fi
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
\&"http://site.{one,two,three}.com"
.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
\&"http://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
\&"http://example.com/file[1\-100:10].txt"
\&"http://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.
Switch off globbing with \fI\-g, \-\-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 access and expand environment variables by first importing them. You
select to either require the environment variable to be set or you can provide
a default value in case it is not already set. Plain "\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 it is not set, use
\&"\fI\-\-variable\fP %name=content" or "\fI\-\-variable\fP %name@content".
Example. Get the USER environment variable 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", it can 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\-o, \-\-output\fP or
\fI\-O, \-\-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.
.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 RTMP(S)
The \fBRealtime Messaging Protocol\fP is primarily used to serve streaming media
and curl can download it.
.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 suffixes
(k, M, G, T, P) are 1024 based. For example 1k is 1024 bytes. 1M is 1048576
bytes.
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\-o, \-\-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\-s, \-\-silent\fP option.
.SH VERSION
This man page describes curl 8.14.1. 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\-d, \-\-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\-". However, in this list we mostly only list and 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.
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.
The following options are global: \fI\-\-fail\-early\fP, \fI\-\-libcurl\fP, \fI\-\-parallel\-immediate\fP, \fI\-\-parallel\-max\fP, \fI\-Z, \-\-parallel\fP, \fI\-#, \-\-progress\-bar\fP, \fI\-\-rate\fP, \fI\-S, \-\-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\-v, \-\-verbose\fP.
.SH ALL OPTIONS
.IP "\-\-abstract\-unix\-socket <path>"
(HTTP) Connect 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 --abstract-unix-socket 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 just
handle the cache in memory.
If this option is used several times, curl loads contents from all the
files but the last one is used for saving.
--alt-svc can be used several times in a command line
Example:
.nf
curl --alt-svc svc.txt https://example.com
.fi
Added in 7.64.1. 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\-u, \-\-user\fP.
Providing --anyauth multiple times has no extra effect.
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 --append 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-r, \-\-range\fP and \fI-C, \-\-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 --aws-sigv4 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-u, \-\-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\-u, \-\-user\fP.
Providing --basic multiple times has no extra effect.
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 (LibreSSL, BoringSSL, etc) on
Windows. (Added in 7.71.0)
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)
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 or Secure Transport. Those are
native TLS libraries from Microsoft and Apple, respectively, that by default
use the native CA store for verification unless overridden by a CA certificate
location setting.
Providing --ca-native 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-k, \-\-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.
(iOS and macOS only) If curl is built against Secure Transport, then this
option is supported for backward compatibility with other SSL engines, but it
should not be set. If the option is not set, then curl uses the certificates
in the system and user Keychain to verify the peer, which is the preferred
method of verifying the peer\(aqs certificate chain.
(Schannel only) 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 --cacert 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-k, \-\-insecure\fP.
.IP "\-\-capath <dir>"
(TLS) Use the specified certificate directory to verify the peer. 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\-\-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 --capath 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-k, \-\-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 in PKCS#12 format if
using Secure Transport, or PEM format if using any other engine. 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\-E, \-\-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.
(iOS and macOS only) If curl is built against Secure Transport, then the
certificate string can either be the name of a certificate/private key in the
system or user keychain, or the path to a PKCS#12\-encoded certificate and
private key. If you want to use a file from the current directory, please
precede it with "./" prefix, in order to avoid confusion with a nickname.
(Schannel only) 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 --cert 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 --cert-status 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, however for
Secure Transport and Schannel it is P12. If \fI\-E, \-\-cert\fP is a pkcs11: URI then ENG
or PROV is the default type (depending on OpenSSL version).
If --cert-type 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-E, \-\-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 --ciphers 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.
Providing --compressed 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.
Providing --compressed-ssh 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\-K, \-\-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 simply writing the URL on its own
line. So, 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\-q, \-\-disable\fP is used) checks for a default
config file and uses it if found, even when \fI\-K, \-\-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.
--config can be used several times in a command line
Example:
.nf
curl --config file.txt https://example.com
.fi
See also \fI-q, \-\-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 --connect-timeout 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-m, \-\-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 host name 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
--connect-to 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-H, \-\-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\-r, \-\-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\-C, \-\-continue\-at\fP.
If --continue-at 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-r, \-\-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\-L, \-\-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\-b, \-\-cookie\fP is only used as input. No cookies are written
to that file. To store cookies, use the \fI\-c, \-\-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\-b, \-\-cookie\fP and \fI\-c, \-\-cookie\-jar\fP in the same command
line is common.
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.
--cookie 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-c, \-\-cookie\-jar\fP and \fI-j, \-\-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\-c, \-\-cookie\-jar\fP is only used for output. No cookies are
read from the file. To read cookies, use the \fI\-b, \-\-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\-b, \-\-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\-v, \-\-verbose\fP gets a warning
displayed, but that is the only visible feedback you get about this possibly
lethal situation.
If --cookie-jar 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-b, \-\-cookie\fP and \fI-j, \-\-junk\-session\-cookies\fP.
.IP "\-\-create\-dirs"
When used in conjunction with the \fI\-o, \-\-output\fP option, curl creates the necessary
local directory hierarchy as needed. This option creates the directories
mentioned with the \fI\-o, \-\-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 --create-dirs 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 --create-file-mode 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 --crlf 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-B, \-\-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 --crlfile 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 --curves 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\-F, \-\-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\-d, \-\-data\fP @foobar. When \fI\-d, \-\-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.
--data 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-F, \-\-form\fP, \fI-I, \-\-head\fP and \fI-T, \-\-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 just an alias for \fI\-d, \-\-data\fP.
--data-ascii 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\-d, \-\-data\fP does, except that newlines and carriage returns are
preserved and conversions are never done.
Like \fI\-d, \-\-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\-d, \-\-data\fP.
--data-binary 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\-d, \-\-data\fP but without the special interpretation of the @
character.
--data-raw 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-d, \-\-data\fP.
.IP "\-\-data\-urlencode <data>"
(HTTP) Post data, similar to the other \fI\-d, \-\-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. Just 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
--data-urlencode 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-d, \-\-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 --delegation is provided several times, the last set value is used.
Example:
.nf
curl --delegation "none" https://example.com
.fi
See also \fI-k, \-\-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\-u, \-\-user\fP option to set username and password.
Providing --digest multiple times has no extra effect.
Disable it again with \-\-no-digest.
Example:
.nf
curl -u name:password --digest https://example.com
.fi
This option is mutually exclusive with \fI\-\-basic\fP, \fI\-\-ntlm\fP and \fI\-\-negotiate\fP.
See also \fI-u, \-\-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\-K, \-\-config\fP for details on the default config
file search path.
Providing --disable multiple times has no extra effect.
Disable it again with \-\-no-disable.
Example:
.nf
curl -q https://example.com
.fi
See also \fI-K, \-\-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\-P, \-\-ftp\-port\fP or force it with \fI\-\-ftp\-pasv\fP.
Providing --disable-eprt 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-P, \-\-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\-P, \-\-ftp\-port\fP.
Providing --disable-epsv 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-P, \-\-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.
Providing --disallow-username-in-url 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
Added in 7.61.0. 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 --dns-interface is provided several times, the last set value is used.
Example:
.nf
curl --dns-interface eth0 https://example.com
.fi
\fI\-\-dns\-interface\fP requires that 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 --dns-ipv4-addr is provided several times, the last set value is used.
Example:
.nf
curl --dns-ipv4-addr 10.1.2.3 https://example.com
.fi
\fI\-\-dns\-ipv4\-addr\fP requires that 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 --dns-ipv6-addr is provided several times, the last set value is used.
Example:
.nf
curl --dns-ipv6-addr 2a04:4e42::561 https://example.com
.fi
\fI\-\-dns\-ipv6\-addr\fP requires that 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 --dns-servers 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
\fI\-\-dns\-servers\fP requires that libcurl is built to support c-ares.
See also \fI\-\-dns\-interface\fP and \fI\-\-dns\-ipv4\-addr\fP.
.IP "\-\-doh\-cert\-status"
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 --doh-cert-status 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"
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\-k, \-\-insecure\fP and \fI\-\-proxy\-insecure\fP but used for DoH
(DNS\-over\-HTTPS) only.
Providing --doh-insecure 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-k, \-\-insecure\fP and \fI\-\-proxy\-insecure\fP.
.IP "\-\-doh\-url <URL>"
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. However, 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 --doh-url 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
Added in 7.62.0. 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 --dump-ca-embed 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\-D, \-\-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 --dump-header 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-o, \-\-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 --ech 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 --egd-file 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.
If --engine 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 --etag-compare 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-z, \-\-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 --etag-save 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 --expect100-timeout 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 --fail 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\-f, \-\-fail\fP, which causes transfers to fail due to the
server\(aqs HTTP status code. You can combine the two options, however note \fI\-f, \-\-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 --next.
Providing --fail-early 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-f, \-\-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\-f, \-\-fail\fP which makes curl fail for the same
circumstances but without saving the content.
Providing --fail-with-body 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-f, \-\-fail\fP.
Added in 7.76.0. See also \fI-f, \-\-fail\fP and \fI\-\-fail\-early\fP.
.IP "\-\-false\-start"
(TLS) 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.
This functionality is currently only implemented in the Secure Transport (on
iOS 7.0 or later, or macOS 10.9 or later) backend.
Providing --false-start 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 "\-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 just 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 just 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
See further examples and details in the MANUAL.
--form 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-d, \-\-data\fP, \fI-I, \-\-head\fP and \fI-T, \-\-upload\-file\fP.
See also \fI-d, \-\-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 --form-escape 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-F, \-\-form\fP.
.IP "\-\-form\-string <name=string>"
(HTTP SMTP IMAP) Similar to \fI\-F, \-\-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\-F, \-\-form\fP if there is any
possibility that the string value may accidentally trigger the @ or <
features of \fI\-F, \-\-form\fP.
--form-string can be used several times in a command line
Example:
.nf
curl --form-string "name=data" https://example.com
.fi
See also \fI-F, \-\-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 --ftp-account is provided several times, the last set value is used.
Example:
.nf
curl --ftp-account "mr.robot" ftp://example.com/
.fi
See also \fI-u, \-\-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 --ftp-alternative-to-user 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-u, \-\-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 --ftp-create-dirs 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 --ftp-method 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-l, \-\-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\-P, \-\-ftp\-port\fP
option.
Reversing an enforced passive really is not doable but you must then instead
enforce the correct \fI\-P, \-\-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 --ftp-pasv multiple times has no extra effect.
Disable it again with \-\-no-ftp-pasv.
Example:
.nf
curl --ftp-pasv ftp://example.com/
.fi
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 --ftp-port 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 --ftp-pret 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-P, \-\-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 --ftp-skip-pasv-ip 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 --ftp-ssl-ccc 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 --ftp-ssl-ccc-mode 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.
Providing --ftp-ssl-control 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\-d, \-\-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\-I, \-\-head\fP, the POST data is instead appended to the
URL with a HEAD request.
Providing --get 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-d, \-\-data\fP and \fI-X, \-\-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.
Providing --globoff multiple times has no extra effect.
Disable it again with \-\-no-globoff.
Example:
.nf
curl -g "https://example.com/{[]}}}}"
.fi
See also \fI-K, \-\-config\fP and \fI-q, \-\-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 --happy-eyeballs-timeout-ms 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-m, \-\-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 --haproxy-clientip 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-x, \-\-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 --haproxy-protocol multiple times has no extra effect.
Disable it again with \-\-no-haproxy-protocol.
Example:
.nf
curl --haproxy-protocol https://example.com
.fi
Added in 7.60.0. See also \fI-x, \-\-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 --head multiple times has no extra effect.
Disable it again with \-\-no-head.
Example:
.nf
curl -I https://example.com
.fi
See also \fI-G, \-\-get\fP, \fI-v, \-\-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\-F, \-\-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\-L, \-\-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.
--header 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-A, \-\-user\-agent\fP and \fI-e, \-\-referer\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-v, \-\-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 --hostpubmd5 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.
This feature requires libcurl to be built with libssh2 and does not work with
other SSH backends.
If --hostpubsha256 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 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 just
handle HSTS in memory.
If this option is used several times, curl loads contents from all the
files but the last one is used for saving.
--hsts 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 simply
transparently downgrades \- if allowed.
HTTP/0.9 is disabled by default (added in 7.66.0)
Providing --http0.9 multiple times has no extra effect.
Disable it again with \-\-no-http0.9.
Example:
.nf
curl --http0.9 https://example.com
.fi
Added in 7.64.0. 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 --http1.0 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 --http1.1 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 --http2 multiple times has no extra effect.
Example:
.nf
curl --http2 https://example.com
.fi
\fI\-\-http2\fP requires that 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 and \fI\-\-no\-alpn\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 --http2-prior-knowledge multiple times has no extra effect.
Disable it again with \-\-no-http2-prior-knowledge.
Example:
.nf
curl --http2-prior-knowledge https://example.com
.fi
\fI\-\-http2\-prior\-knowledge\fP requires that 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.
Providing --http3 multiple times has no extra effect.
Example:
.nf
curl --http3 https://example.com
.fi
\fI\-\-http3\fP requires that 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 --http3-only multiple times has no extra effect.
Example:
.nf
curl --http3-only https://example.com
.fi
\fI\-\-http3\-only\fP requires that 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 --ignore-content-length 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\-k, \-\-insecure\fP can make curl trust and use such information from malicious
servers.
Providing --insecure 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 --interface 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>"
(All) 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 --ip-tos 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 --ipfs-gateway 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-h, \-\-help\fP and \fI-M, \-\-manual\fP.
.IP "\-4, \-\-ipv4"
Use IPv4 addresses only when resolving hostnames, and not for example try
IPv6.
Providing --ipv4 multiple times has no extra effect.
Example:
.nf
curl --ipv4 https://example.com
.fi
This option is mutually exclusive with \fI-6, \-\-ipv6\fP.
See also \fI\-\-http1.1\fP and \fI\-\-http2\fP.
.IP "\-6, \-\-ipv6"
Use IPv6 addresses only when resolving hostnames, and not for example try
IPv4.
Your resolver may 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 --ipv6 multiple times has no extra effect.
Example:
.nf
curl --ipv6 https://example.com
.fi
This option is mutually exclusive with \fI-4, \-\-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\-H, \-\-header\fP as usual.
--json can be used several times in a command line
Examples:
.nf
curl --json '{ "drink": "coffe" }' https://example.com
curl --json '{ "drink":' --json ' "coffe" }' https://example.com
curl --json @prepared https://example.com
curl --json @- https://example.com < json.txt
.fi
This option is mutually exclusive with \fI-F, \-\-form\fP, \fI-I, \-\-head\fP and \fI-T, \-\-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.
Providing --junk-session-cookies 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-b, \-\-cookie\fP and \fI-c, \-\-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 --keepalive-cnt 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 --keepalive-time 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-m, \-\-max\-time\fP.
.IP "\-\-key <key>"
(TLS SSH) 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 Secure Transport or Schannel then this option is
ignored for TLS protocols (HTTPS, etc). Those backends expect the private key
to be already present in the keychain or PKCS#12 file containing the
certificate.
If --key 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-E, \-\-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 --key-type 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 "\-\-krb <level>"
(FTP) Enable Kerberos authentication and use. The level must be entered and should
be one of \(aqclear\(aq, \(aqsafe\(aq, \(aqconfidential\(aq, or \(aqprivate\(aq. Should you use a
level that is not one of these, \(aqprivate\(aq is used.
If --krb is provided several times, the last set value is used.
Example:
.nf
curl --krb clear ftp://example.com/
.fi
\fI\-\-krb\fP requires that 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 --next.
If --libcurl is provided several times, the last set value is used.
Example:
.nf
curl --libcurl client.c https://example.com
.fi
See also \fI-v, \-\-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, while \(aqg\(aq or \(aqG\(aq makes it gigabytes. The 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\-Y, \-\-speed\-limit\fP option, that option takes precedence and
might cripple the rate\-limiting slightly, to help keep the speed\-limit
logic working.
If --limit-rate is provided several times, the last set value is used.
Examples:
.nf
curl --limit-rate 100K https://example.com
curl --limit-rate 1000 https://example.com
curl --limit-rate 10M https://example.com
.fi
See also \fI\-\-rate\fP, \fI-Y, \-\-speed\-limit\fP and \fI-y, \-\-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 sub\-directories 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 just 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\-X, \-\-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 --list-only 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-Q, \-\-quote\fP and \fI-X, \-\-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 --local-port is provided several times, the last set value is used.
Example:
.nf
curl --local-port 1000-3000 https://example.com
.fi
See also \fI-g, \-\-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\-i, \-\-show\-headers\fP or \fI\-I, \-\-head\fP, headers from all requested pages are shown.
When authentication is used, 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.
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\-X, \-\-request\fP overrides the method curl would otherwise select
to use.
Providing --location 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 and \fI\-\-alt\-svc\fP.
.IP "\-\-location\-trusted"
(HTTP) Instruct curl to follow HTTP redirects like \fI\-L, \-\-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\-H, \-\-header\fP.
Providing --location-trusted 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-u, \-\-user\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 --login-options is provided several times, the last set value is used.
Example:
.nf
curl --login-options 'AUTH=*' imap://example.com
.fi
See also \fI-u, \-\-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 --mail-auth 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 --mail-from 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".
--mail-rcpt 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 --mail-rcpt-allowfails 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-v, \-\-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 size modifier may be used. For example, Appending \(aqk\(aq or \(aqK\(aq counts the
number as kilobytes, \(aqm\(aq or \(aqM\(aq makes it megabytes, while \(aqg\(aq or \(aqG\(aq makes it
gigabytes. 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.
If --max-filesize is provided several times, the last set value is used.
Example:
.nf
curl --max-filesize 100K 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\-L, \-\-location\fP is used, to
prevent 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 --max-redirs is provided several times, the last set value is used.
Example:
.nf
curl --max-redirs 3 --location https://example.com
.fi
See also \fI-L, \-\-location\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 --max-time 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 --metalink is provided several times, the last set value is used.
Example:
.nf
curl --metalink file https://example.com
.fi
See also \fI-Z, \-\-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 --mptcp 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\-V, \-\-version\fP to see if your curl supports GSS\-API/SSPI or SPNEGO.
When using this option, you must also provide a fake \fI\-u, \-\-user\fP option to activate
the authentication code properly. Sending a \(aq\-u :\(aq is enough as the username
and password from the \fI\-u, \-\-user\fP option are not actually used.
Providing --negotiate multiple times has no extra effect.
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.
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 FTP to
the machine host.example.com with username \(aqmyself\(aq and password \(aqsecret\(aq could
look similar to:
.nf
machine host.example.com
login myself
password secret
.fi
Providing --netrc 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-K, \-\-config\fP and \fI-u, \-\-user\fP.
.IP "\-\-netrc\-file <filename>"
Set the netrc file to use. Similar to \fI\-n, \-\-netrc\fP, except that you also provide
the path (absolute or relative).
It abides by \fI\-\-netrc\-optional\fP if specified.
If --netrc-file 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-n, \-\-netrc\fP.
See also \fI-n, \-\-netrc\fP, \fI-u, \-\-user\fP and \fI-K, \-\-config\fP.
.IP "\-\-netrc\-optional"
Similar to \fI\-n, \-\-netrc\fP, but this option makes the .netrc usage \fBoptional\fP
and not mandatory as the \fI\-n, \-\-netrc\fP option does.
Providing --netrc-optional 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-n, \-\-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\-v, \-\-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
--next 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-Z, \-\-parallel\fP and \fI-K, \-\-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 --no-alpn multiple times has no extra effect.
Disable it again with \-\-alpn.
Example:
.nf
curl --no-alpn https://example.com
.fi
\fI\-\-no\-alpn\fP requires that 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 --no-buffer 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\-o, \-\-output\fP, \fI\-J, \-\-remote\-header\-name\fP,
\fI\-O, \-\-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\-J, \-\-remote\-header\-name\fP is
specified.
The \fI\-C, \-\-continue\-at\fP option cannot be used together with \fI\-\-no\-clobber\fP.
Providing --no-clobber 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-o, \-\-output\fP and \fI-O, \-\-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 --no-keepalive 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 --no-npn multiple times has no extra effect.
Disable it again with \-\-npn.
Example:
.nf
curl --no-npn https://example.com
.fi
\fI\-\-no\-npn\fP requires that 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\-s, \-\-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 --no-progress-meter 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-v, \-\-verbose\fP and \fI-s, \-\-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 --no-sessionid multiple times has no extra effect.
Disable it again with \-\-sessionid.
Example:
.nf
curl --no-sessionid https://example.com
.fi
See also \fI-k, \-\-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".
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 --noproxy is provided several times, the last set value is used.
Example:
.nf
curl --noproxy "www.example" https://example.com
.fi
See also \fI-x, \-\-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 --ntlm multiple times has no extra effect.
Example:
.nf
curl --ntlm -u user:password https://example.com
.fi
\fI\-\-ntlm\fP requires that libcurl is built to support TLS.
This option is mutually exclusive with \fI\-\-basic\fP, \fI\-\-negotiate\fP, \fI\-\-digest\fP and \fI\-\-anyauth\fP.
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 --ntlm-wb 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\-u, \-\-user\fP options.
The Bearer Token and username are formatted according to RFC 6750.
If --oauth2-bearer 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 "\-o, \-\-output <file>"
Write output to the given file instead of stdout. If you are using globbing to
fetch multiple documents, you should quote the URL and you can use "#"
followed by a number in the filename. That variable is then replaced with the
current string for the URL being fetched. 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, just 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
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
--output 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-O, \-\-remote\-name\fP, \fI\-\-remote\-name\-all\fP and \fI-J, \-\-remote\-header\-name\fP.
.IP "\-\-output\-dir <dir>"
Specify the directory in which files should be stored, when \fI\-O, \-\-remote\-name\fP or
\fI\-o, \-\-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 --output-dir 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-O, \-\-remote\-name\fP and \fI-J, \-\-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 --next.
Providing --parallel 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-v, \-\-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 --next.
Providing --parallel-immediate 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-Z, \-\-parallel\fP and \fI\-\-parallel\-max\fP.
.IP "\-\-parallel\-max <num>"
When asked to do parallel transfers, using \fI\-Z, \-\-parallel\fP, this option controls
the maximum amount of transfers to do simultaneously.
The default is 50. 300 is the largest supported value.
This option is global and does not need to be specified for each use of --next.
If --parallel-max 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-Z, \-\-parallel\fP.
.IP "\-\-pass <phrase>"
(SSH TLS) Passphrase for the private key used for SSH or TLS.
If --pass 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-u, \-\-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 --path-as-is 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\-k, \-\-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,
Secure Transport macOS 10.7+/iOS 10+,
Schannel
sha256 support:
OpenSSL, GnuTLS and wolfSSL, mbedTLS,
Secure Transport macOS 10.7+/iOS 10+, Schannel
Other SSL backends not supported.
If --pinnedpubkey 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. However, a
server may require a POST to remain a POST after such a redirection. This
option is meaningful only when using \fI\-L, \-\-location\fP.
Providing --post301 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-L, \-\-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. However, a
server may require a POST to remain a POST after such a redirection. This
option is meaningful only when using \fI\-L, \-\-location\fP.
Providing --post302 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-L, \-\-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\-L, \-\-location\fP.
Providing --post303 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-L, \-\-location\fP.
.IP "\-\-preproxy <[protocol://]host[:port]>"
Use the specified SOCKS proxy before connecting to an HTTP or HTTPS \fI\-x, \-\-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 --preproxy 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-x, \-\-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 --next.
Providing --progress-bar 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 --proto 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.
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.
If --proto-default 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 http://example.com
.fi
By default curl only allows HTTP, HTTPS, FTP and FTPS on redirects
(added in 7.65.2). Specifying \fIall\fP or \fI+all\fP enables all protocols on
redirects, which is not good for security.
If --proto-redir is provided several times, the last set value is used.
Example:
.nf
curl --proto-redir =http,https https://example.com
.fi
See also \fI\-\-proto\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 BearSSL, mbedTLS, Rustls,
Schannel, Secure Transport and wolfSSL (added in 7.87.0).
Unrecognized and unsupported proxy protocols cause an error.
Ancient curl versions ignored unknown schemes and used http:// instead.
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\-p, \-\-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\-P, \-\-ftp\-port\fP, cannot be
used.
Doing FTP over an HTTP proxy without \fI\-p, \-\-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 --proxy 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.
Providing --proxy-anyauth multiple times has no extra effect.
Example:
.nf
curl --proxy-anyauth --proxy-user user:passwd -x proxy https://example.com
.fi
See also \fI-x, \-\-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 --proxy-basic multiple times has no extra effect.
Example:
.nf
curl --proxy-basic --proxy-user user:passwd -x proxy https://example.com
.fi
See also \fI-x, \-\-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 --proxy-ca-native 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-k, \-\-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 --proxy-cacert is provided several times, the last set value is used.
Example:
.nf
curl --proxy-cacert CA-file.txt -x https://proxy https://example.com
.fi
See also \fI\-\-proxy\-capath\fP, \fI\-\-cacert\fP, \fI\-\-capath\fP, \fI\-\-dump\-ca\-embed\fP and \fI-x, \-\-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 --proxy-capath is provided several times, the last set value is used.
Example:
.nf
curl --proxy-capath /local/directory -x https://proxy https://example.com
.fi
See also \fI\-\-proxy\-cacert\fP, \fI-x, \-\-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 in PKCS#12 format if using Secure Transport, or
PEM format if using any other engine. 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\-E, \-\-cert\fP but used in HTTPS proxy context.
If --proxy-cert is provided several times, the last set value is used.
Example:
.nf
curl --proxy-cert file -x https://proxy https://example.com
.fi
See also \fI-x, \-\-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, however for
Secure Transport and 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 --proxy-cert-type is provided several times, the last set value is used.
Example:
.nf
curl --proxy-cert-type PEM --proxy-cert file -x https://proxy 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 --proxy-ciphers 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 https://example.com
.fi
See also \fI\-\-proxy\-tls13\-ciphers\fP, \fI\-\-ciphers\fP and \fI-x, \-\-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 --proxy-crlfile is provided several times, the last set value is used.
Example:
.nf
curl --proxy-crlfile rejects.txt -x https://proxy https://example.com
.fi
See also \fI\-\-crlfile\fP and \fI-x, \-\-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 --proxy-digest multiple times has no extra effect.
Example:
.nf
curl --proxy-digest --proxy-user user:passwd -x proxy https://example.com
.fi
See also \fI-x, \-\-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\-H, \-\-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.
--proxy-header 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-x, \-\-proxy\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.
Providing --proxy-http2 multiple times has no extra effect.
Disable it again with \-\-no-proxy-http2.
Example:
.nf
curl --proxy-http2 -x proxy https://example.com
.fi
\fI\-\-proxy\-http2\fP requires that libcurl is built to support HTTP/2.
Added in 8.1.0. See also \fI-x, \-\-proxy\fP.
.IP "\-\-proxy\-insecure"
Same as \fI\-k, \-\-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 --proxy-insecure multiple times has no extra effect.
Disable it again with \-\-no-proxy-insecure.
Example:
.nf
curl --proxy-insecure -x https://proxy https://example.com
.fi
See also \fI-x, \-\-proxy\fP and \fI-k, \-\-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 --proxy-key is provided several times, the last set value is used.
Example:
.nf
curl --proxy-key here -x https://proxy https://example.com
.fi
See also \fI\-\-proxy\-key\-type\fP and \fI-x, \-\-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 --proxy-key-type is provided several times, the last set value is used.
Example:
.nf
curl --proxy-key-type DER --proxy-key here -x https://proxy https://example.com
.fi
See also \fI\-\-proxy\-key\fP and \fI-x, \-\-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 --proxy-negotiate 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 --proxy-ntlm multiple times has no extra effect.
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-U, \-\-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 --proxy-pass is provided several times, the last set value is used.
Example:
.nf
curl --proxy-pass secret --proxy-key here -x https://proxy https://example.com
.fi
See also \fI-x, \-\-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 --proxy-pinnedpubkey 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-x, \-\-proxy\fP.
.IP "\-\-proxy\-service\-name <name>"
Set the service name for SPNEGO when doing proxy authentication.
If --proxy-service-name 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-x, \-\-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 --proxy-ssl-allow-beast 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 https://example.com
.fi
See also \fI\-\-ssl\-allow\-beast\fP and \fI-x, \-\-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 --proxy-ssl-auto-client-cert 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 https://example.com
.fi
Added in 7.77.0. See also \fI\-\-ssl\-auto\-client\-cert\fP and \fI-x, \-\-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 --proxy-tls13-ciphers 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
Added in 7.61.0. See also \fI\-\-proxy\-ciphers\fP, \fI\-\-tls13\-ciphers\fP and \fI-x, \-\-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 --proxy-tlsauthtype is provided several times, the last set value is used.
Example:
.nf
curl --proxy-tlsauthtype SRP -x https://proxy https://example.com
.fi
See also \fI-x, \-\-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 --proxy-tlspassword is provided several times, the last set value is used.
Example:
.nf
curl --proxy-tlspassword passwd -x https://proxy https://example.com
.fi
See also \fI-x, \-\-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 --proxy-tlsuser is provided several times, the last set value is used.
Example:
.nf
curl --proxy-tlsuser smith -x https://proxy https://example.com
.fi
See also \fI-x, \-\-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\-1, \-\-tlsv1\fP but for an HTTPS proxy context.
Providing --proxy-tlsv1 multiple times has no extra effect.
Example:
.nf
curl --proxy-tlsv1 -x https://proxy https://example.com
.fi
See also \fI-x, \-\-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 --proxy-user 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\-x, \-\-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 --proxy1.0 multiple times has no extra effect.
Example:
.nf
curl --proxy1.0 http://proxy https://example.com
.fi
See also \fI-x, \-\-proxy\fP, \fI\-\-socks5\fP and \fI\-\-preproxy\fP.
.IP "\-p, \-\-proxytunnel"
When an HTTP proxy is used \fI\-x, \-\-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 --proxytunnel 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-x, \-\-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 --pubkey 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 (just 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, just before the file transfer command(s), prefix the command with a
\(aq+\(aq. This is not performed when a directory listing is performed.
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 may be quoted shell\-style
to embed spaces or special characters. 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
--quote can be used several times in a command line
Example:
.nf
curl --quote "DELE file" ftp://example.com/foo
.fi
See also \fI-X, \-\-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 --random-file 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\-C, \-\-continue\-at\fP: you can only
use one of them for a single transfer.
If --range is provided several times, the last set value is used.
Example:
.nf
curl --range 22-44 https://example.com
.fi
See also \fI-C, \-\-continue\-at\fP and \fI-a, \-\-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\-Z, \-\-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 --next.
If --rate 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 --raw 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\-H, \-\-header\fP flag of course. When used with \fI\-L, \-\-location\fP you can append ";auto"" to
the \fI\-e, \-\-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\-e, \-\-referer\fP.
If --referer 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-A, \-\-user\-agent\fP and \fI-H, \-\-header\fP.
.IP "\-J, \-\-remote\-header\-name"
(HTTP) Tell the \fI\-O, \-\-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).
\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 --remote-header-name 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-O, \-\-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\-J, \-\-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.
--remote-name 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-J, \-\-remote\-header\-name\fP.
.IP "\-\-remote\-name\-all"
Change the default action for all given URLs to be dealt with as if
\fI\-O, \-\-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 --remote-name-all 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-O, \-\-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 --remote-time 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-O, \-\-remote\-name\fP and \fI-z, \-\-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\-C, \-\-continue\-at\fP option cannot be used together with \fI\-\-remove\-on\-error\fP.
Providing --remove-on-error 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-f, \-\-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\-I, \-\-head\fP option.
The method string you set with \fI\-X, \-\-request\fP is used for all requests, which
if you for example use \fI\-L, \-\-location\fP may cause unintended side\-effects when curl
does not change request method according to the HTTP 30x response codes \- and
similar.
.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 --request is provided several times, the last set value is used.
Examples:
.nf
curl -X "DELETE" https://example.com
curl -X NLST ftp://example.com/
.fi
See also \fI\-\-request\-target\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 --request-target is provided several times, the last set value is used.
Example:
.nf
curl --request-target "*" -X OPTIONS https://example.com
.fi
See also \fI-X, \-\-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\-4, \-\-ipv4\fP or \fI\-6, \-\-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.
--resolve 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 or 504
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 --retry 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.
.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\-f, \-\-fail\fP.
Providing --retry-all-errors 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, consider ECONNREFUSED as a transient
error too for \fI\-\-retry\fP. This option is used together with \fI\-\-retry\fP.
Providing --retry-connrefused 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.
If --retry-delay 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.
.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\-m, \-\-max\-time\fP. Set this option to zero
to not timeout retries.
If --retry-max-time 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.
.IP "\-\-sasl\-authzid <identity>"
Use this authorization identity (\fBauthzid\fP), during SASL PLAIN
authentication, in addition to the authentication identity (\fBauthcid\fP) as
specified by \fI\-u, \-\-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 --sasl-authzid 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"
Enable initial response in SASL authentication.
Providing --sasl-ir 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 --service-name 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\-s, \-\-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 --next.
Providing --show-error 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\-D, \-\-dump\-header\fP exists to save headers in a separate stream.
To view the request headers, consider the \fI\-v, \-\-verbose\fP option.
Prior to 7.75.0 curl did not print the headers if \fI\-f, \-\-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 --show-headers multiple times has no extra effect.
Disable it again with \-\-no-show-headers.
Example:
.nf
curl -i https://example.com
.fi
See also \fI-v, \-\-verbose\fP and \fI-D, \-\-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 --sigalgs 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 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\-S, \-\-show\-error\fP in addition to this option to disable progress meter but
still show error messages.
Providing --silent multiple times has no extra effect.
Disable it again with \-\-no-silent.
Example:
.nf
curl -s https://example.com
.fi
See also \fI-v, \-\-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 just knows if there is a
filename present in the file system or not and it skips the transfer if it is.
Providing --skip-existing 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-o, \-\-output\fP, \fI-O, \-\-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 proxy on a Unix domain socket, use localhost for host, e.g.
\&"socks4://localhost/path/to/socket.sock"
This option overrides any previous use of \fI\-x, \-\-proxy\fP, as they are mutually
exclusive.
This option is superfluous since you can specify a socks4 proxy with \fI\-x, \-\-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 --socks4 is provided several times, the last set value is used.
Example:
.nf
curl --socks4 hostname:4096 https://example.com
.fi
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 proxy on a Unix domain socket, use localhost for host, e.g.
\&"socks4a://localhost/path/to/socket.sock"
This option overrides any previous use of \fI\-x, \-\-proxy\fP, as they are mutually
exclusive.
This option is superfluous since you can specify a socks4a proxy with \fI\-x, \-\-proxy\fP
using a socks4a:// protocol prefix.
\fI\-\-preproxy\fP can be used to specify a SOCKS proxy at the same time \fI\-x, \-\-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 --socks4a is provided several times, the last set value is used.
Example:
.nf
curl --socks4a hostname:4096 https://example.com
.fi
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 proxy on a Unix domain socket, use localhost for host, e.g.
\&"socks5://localhost/path/to/socket.sock"
This option overrides any previous use of \fI\-x, \-\-proxy\fP, as they are mutually
exclusive.
This option is superfluous since you can specify a socks5 proxy with \fI\-x, \-\-proxy\fP
using a socks5:// protocol prefix.
\fI\-\-preproxy\fP can be used to specify a SOCKS proxy at the same time \fI\-x, \-\-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 --socks5 is provided several times, the last set value is used.
Example:
.nf
curl --socks5 proxy.example:7000 https://example.com
.fi
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 --socks5-basic 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"
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 --socks5-gssapi 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"
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 --socks5-gssapi-nec 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 --socks5-gssapi-service 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 proxy on a Unix domain socket, use localhost for host, e.g.
\&"socks5h://localhost/path/to/socket.sock"
This option overrides any previous use of \fI\-x, \-\-proxy\fP, as they are mutually
exclusive.
This option is superfluous since you can specify a socks5 hostname proxy with
\fI\-x, \-\-proxy\fP using a socks5h:// protocol prefix.
\fI\-\-preproxy\fP can be used to specify a SOCKS proxy at the same time \fI\-x, \-\-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 --socks5-hostname is provided several times, the last set value is used.
Example:
.nf
curl --socks5-hostname proxy.example:7000 https://example.com
.fi
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\-y, \-\-speed\-time\fP
and is 30 seconds by default.
If --speed-limit 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-y, \-\-speed\-time\fP, \fI\-\-limit\-rate\fP and \fI-m, \-\-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\-Y, \-\-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 --speed-time 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-Y, \-\-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 does
not succeed.
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 --ssl 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-k, \-\-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 --ssl-allow-beast 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-k, \-\-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 --ssl-auto-client-cert 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 --ssl-no-revoke 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 --ssl-reqd 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-k, \-\-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 --ssl-revoke-best-effort 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-k, \-\-insecure\fP.
.IP "\-\-ssl\-sessions <filename>"
(TLS) 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.
If --ssl-sessions 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 --sslv2 multiple times has no extra effect.
Example:
.nf
curl --sslv2 https://example.com
.fi
\fI-2, \-\-sslv2\fP requires that libcurl is built to support TLS.
This option is mutually exclusive with \fI-3, \-\-sslv3\fP, \fI-1, \-\-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 --sslv3 multiple times has no extra effect.
Example:
.nf
curl --sslv3 https://example.com
.fi
\fI-3, \-\-sslv3\fP requires that libcurl is built to support TLS.
This option is mutually exclusive with \fI-2, \-\-sslv2\fP, \fI-1, \-\-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 --next.
If --stderr is provided several times, the last set value is used.
Example:
.nf
curl --stderr output.txt https://example.com
.fi
See also \fI-v, \-\-verbose\fP and \fI-s, \-\-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 --next.
Providing --styled-output multiple times has no extra effect.
Disable it again with \-\-no-styled-output.
Example:
.nf
curl --styled-output -I https://example.com
.fi
Added in 7.61.0. See also \fI-I, \-\-head\fP and \fI-v, \-\-verbose\fP.
.IP "\-\-suppress\-connect\-headers"
When \fI\-p, \-\-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\-D, \-\-dump\-header\fP
or \fI\-i, \-\-show\-headers\fP which are used to show protocol headers in the output. It
has no effect on debug options such as \fI\-v, \-\-verbose\fP or \fI\-\-trace\fP, or any
statistics.
Providing --suppress-connect-headers 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-D, \-\-dump\-header\fP, \fI-i, \-\-show\-headers\fP and \fI-p, \-\-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 --tcp-fastopen 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. See the \fIcurl_easy_setopt(3)\fP man page for
details about this option.
curl sets this option by default and you need to explicitly switch it off if
you do not want it on.
Providing --tcp-nodelay 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-N, \-\-no\-buffer\fP.
.IP "\-t, \-\-telnet\-option <opt=val>"
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
--telnet-option can be used several times in a command line
Example:
.nf
curl -t TTYPE=vt100 telnet://example.com/
.fi
See also \fI-K, \-\-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 --tftp-blksize 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 --tftp-no-options 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 pages 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 --time-cond 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-R, \-\-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 is used when curl is built to use GnuTLS.
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\-w, \-\-write\-out\fP"
variable "tls_earlydata".
\fBWARNING\fP: this option has security implications. See above for more
details.
Providing --tls-earlydata 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 --tls-max 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
\fI\-\-tls\-max\fP requires that 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 --tls13-ciphers is provided several times, the last set value is used.
Example:
.nf
curl --tls13-ciphers TLS_AES_128_GCM_SHA256 https://example.com
.fi
Added in 7.61.0. 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 --tlsauthtype 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 --tlspassword 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 --tlsuser 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 --tlsv1 multiple times has no extra effect.
Example:
.nf
curl --tlsv1 https://example.com
.fi
\fI-1, \-\-tlsv1\fP requires that 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 --tlsv1.0 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 --tlsv1.1 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 --tlsv1.2 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 --tlsv1.3 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.
Providing --tr-encoding 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 --next.
If --trace 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-v, \-\-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 --next.
If --trace-ascii 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-v, \-\-verbose\fP.
See also \fI-v, \-\-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 --next.
--trace-config 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-v, \-\-verbose\fP and \fI\-\-trace\fP.
.IP "\-\-trace\-ids"
Prepend the transfer and connection identifiers to each trace or verbose line
that curl displays.
This option is global and does not need to be specified for each use of --next.
Providing --trace-ids 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-v, \-\-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 --next.
Providing --trace-time 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-v, \-\-verbose\fP.
.IP "\-\-unix\-socket <path>"
(HTTP) Connect through this Unix domain socket, instead of using the network.
If --unix-socket 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\-T, \-\-upload\-file\fP for each URL on the command line. Each
\fI\-T, \-\-upload\-file\fP + URL pair specifies what to upload and to where. curl also
supports globbing of the \fI\-T, \-\-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.
When uploading to an SMTP server: 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.
--upload-file 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-G, \-\-get\fP, \fI-I, \-\-head\fP, \fI-X, \-\-request\fP and \fI-d, \-\-data\fP.
.IP "\-\-upload\-flags <flags>"
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 --upload-flags 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-T, \-\-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\-o, \-\-output\fP or the \fI\-O, \-\-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\-O, \-\-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.
--url 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-K, \-\-config\fP, \fI\-\-path\-as\-is\fP and \fI\-\-disallow\-username\-in\-url\fP.
.IP "\-\-url\-query <data>"
(all) 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.
--url-query 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-G, \-\-get\fP.
.IP "\-B, \-\-use\-ascii"
(FTP LDAP) Enable ASCII transfer mode. For FTP, this can also be enforced by using a URL
that ends with ";type=A". This option causes data sent to stdout to be in text
mode for Win32 systems.
Providing --use-ascii 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\-n, \-\-netrc\fP and \fI\-\-netrc\-optional\fP.
If you simply specify 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 simply as the username, 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 --user is provided several times, the last set value is used.
Example:
.nf
curl -u user:secret https://example.com
.fi
See also \fI-n, \-\-netrc\fP and \fI-K, \-\-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 quote marks. This header can also
be set with the \fI\-H, \-\-header\fP or the \fI\-\-proxy\-header\fP options.
If you give an empty argument to \fI\-A, \-\-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/8.14.1.
If --user-agent is provided several times, the last set value is used.
Example:
.nf
curl -A "Agent 007" https://example.com
.fi
See also \fI-H, \-\-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
--variable 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-K, \-\-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. A line starting with >
means header data sent by curl, < means header data received by curl that is
hidden in normal cases, and a line starting with * means additional info
provided by curl.
If you only want HTTP headers in the output, \fI\-i, \-\-show\-headers\fP or \fI\-D, \-\-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. However, as before, a single
\fI\-v, \-\-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 --next.
Providing --verbose 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-i, \-\-show\-headers\fP, \fI-s, \-\-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 TrackMemory
Debug memory tracking is supported.
.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-h, \-\-help\fP and \fI-M, \-\-manual\fP.
.IP "\-\-vlan\-priority <priority>"
(All) 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 --vlan-priority 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 just 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, Rustls, and Secure Transport 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\-O, \-\-remote\-name\fP or \fI\-o, \-\-output\fP option. It is
most useful in combination with the \fI\-J, \-\-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\-w, \-\-write\-out\fP remarks. (Added in 7.84.0)
.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. (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, Rustls and Secure Transport 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\-w, \-\-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\-w, \-\-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 to for
example 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\-L, \-\-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_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.
.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\-w, \-\-write\-out\fP output is written to standard
error. (Added in 7.63.0)
.IP stdout
From this point on, the \fI\-w, \-\-write\-out\fP output is written to standard output.
This is the default, but can be used to switch back after switching to stderr.
(Added in 7.63.0)
.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 it took from the start until the last byte is sent by libcurl.
In microseconds. (Added in 8.10.0)
.IP time_pretransfer
The time, in seconds, it took from the start until the file transfer was just
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 8.12.0)
.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
If --write-out is provided several times, the last set value is used.
Example:
.nf
curl -w '%{response_code}\\n' https://example.com
.fi
See also \fI-v, \-\-verbose\fP and \fI-I, \-\-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 --xattr 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-R, \-\-remote\-time\fP, \fI-w, \-\-write\-out\fP and \fI-v, \-\-verbose\fP.
.SH FILES
\fI~/.curlrc\fP
Default config file, see \fI\-K, \-\-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.
Using an environment variable to set the proxy has the same effect as using
the \fI\-x, \-\-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\-x, \-\-proxy\fP option. That is
.nf
NO_PROXY=direct.example.com curl \-x http://proxy.example.com
http://direct.example.com
.fi
accesses the target URL directly, and
.nf
NO_PROXY=direct.example.com curl \-x http://proxy.example.com
http://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 <dir>"
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 <dir>"
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): \fBbearssl\fP, \fBgnutls\fP, \fBmbedtls\fP,
\fBopenssl\fP, \fBrustls\fP, \fBschannel\fP, \fBsecure\-transport\fP, \fBwolfssl\fP
.IP "HOME <dir>"
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 "QLOGDIR <directory name>"
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 <dir>"
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 <filename>"
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 <dir>"
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 <dir>"
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\-f, \-\-fail\fP is used.
.IP 23
Write error. curl could not write data to a local filesystem 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/share/man/man1/wcurl.1 0000644 00000007432 15116230430 0011305 0 ustar 00 .\" generated by cd2nroff 0.1 from wcurl.md
.TH wcurl 1 "2025-06-13" 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.
Simply 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. Just beware that you likely
should be using curl directly if your use case is not covered.
By default, \fBwcurl\fP does:
.IP "* Percent-encode whitespaces in URLs;"
.IP "* Download multiple URLs in parallel"
.nf
if the installed curl's version is \>= 7.66.0 (--parallel);
.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
Don\(aqt percent\-decode the output filename, even if the percent\-encoding in the
URL was done by \fBwcurl\fP, e.g.: The URL contained whitespaces.
.IP --dry-run
Do not actually execute curl, just 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. Whitespaces are 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 (if more options are used, this needs to
be the last one in the list):
\fBwcurl \--curl\-options="\--continue\-at \-" example.com/filename.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/doc/alt-curlssl11/FAQ 0000644 00000204560 15116230435 0012174 0 ustar 00 _ _ ____ _
___| | | | _ \| |
/ __| | | | |_) | |
| (__| |_| | _ <| |___
\___|\___/|_| \_\_____|
FAQ
1. Philosophy
1.1 What is cURL?
1.2 What is libcurl?
1.3 What is curl not?
1.4 When will you make curl do XXXX ?
1.5 Who makes curl?
1.6 What do you get for making curl?
1.7 What about CURL from curl.com?
1.8 I have a problem, who do I mail?
1.9 Where do I buy commercial support for curl?
1.10 How many are using curl?
1.11 Why do you not update ca-bundle.crt
1.12 I have a problem, who can I chat with?
1.13 curl's ECCN number?
1.14 How do I submit my patch?
1.15 How do I port libcurl to my OS?
2. Install Related Problems
2.1 configure fails when using static libraries
2.2 Does curl work/build with other SSL libraries?
2.3 How do I upgrade curl.exe in Windows?
2.4 Does curl support SOCKS (RFC 1928) ?
3. Usage Problems
3.1 curl: (1) SSL is disabled, https: not supported
3.2 How do I tell curl to resume a transfer?
3.3 Why does my posting using -F not work?
3.4 How do I tell curl to run custom FTP commands?
3.5 How can I disable the Accept: */* header?
3.6 Does curl support ASP, XML, XHTML or HTML version Y?
3.7 Can I use curl to delete/rename a file through FTP?
3.8 How do I tell curl to follow HTTP redirects?
3.9 How do I use curl in my favorite programming language?
3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP?
3.11 How do I POST with a different Content-Type?
3.12 Why do FTP-specific features over HTTP proxy fail?
3.13 Why do my single/double quotes fail?
3.14 Does curl support JavaScript or PAC (automated proxy config)?
3.15 Can I do recursive fetches with curl?
3.16 What certificates do I need when I use SSL?
3.17 How do I list the root directory of an FTP server?
3.18 Can I use curl to send a POST/PUT and not wait for a response?
3.19 How do I get HTTP from a host using a specific IP address?
3.20 How to SFTP from my user's home directory?
3.21 Protocol xxx not supported or disabled in libcurl
3.22 curl -X gives me HTTP problems
4. Running Problems
4.2 Why do I get problems when I use & or % in the URL?
4.3 How can I use {, }, [ or ] to specify multiple URLs?
4.4 Why do I get downloaded data even though the webpage does not exist?
4.5 Why do I get return code XXX from an HTTP server?
4.5.1 "400 Bad Request"
4.5.2 "401 Unauthorized"
4.5.3 "403 Forbidden"
4.5.4 "404 Not Found"
4.5.5 "405 Method Not Allowed"
4.5.6 "301 Moved Permanently"
4.6 Can you tell me what error code 142 means?
4.7 How do I keep usernames and passwords secret in curl command lines?
4.8 I found a bug
4.9 curl cannot authenticate to a server that requires NTLM?
4.10 My HTTP request using HEAD, PUT or DELETE does not work
4.11 Why do my HTTP range requests return the full document?
4.12 Why do I get "certificate verify failed" ?
4.13 Why is curl -R on Windows one hour off?
4.14 Redirects work in browser but not with curl
4.15 FTPS does not work
4.16 My HTTP POST or PUT requests are slow
4.17 Non-functional connect timeouts on Windows
4.18 file:// URLs containing drive letters (Windows, NetWare)
4.19 Why does not curl return an error when the network cable is unplugged?
4.20 curl does not return error for HTTP non-200 responses
5. libcurl Issues
5.1 Is libcurl thread-safe?
5.2 How can I receive all data into a large memory chunk?
5.3 How do I fetch multiple files with libcurl?
5.4 Does libcurl do Winsock initialization on Win32 systems?
5.5 Does CURLOPT_WRITEDATA and CURLOPT_READDATA work on Win32 ?
5.6 What about Keep-Alive or persistent connections?
5.7 Link errors when building libcurl on Windows
5.8 libcurl.so.X: open failed: No such file or directory
5.9 How does libcurl resolve hostnames?
5.10 How do I prevent libcurl from writing the response to stdout?
5.11 How do I make libcurl not receive the whole HTTP response?
5.12 Can I make libcurl fake or hide my real IP address?
5.13 How do I stop an ongoing transfer?
5.14 Using C++ non-static functions for callbacks?
5.15 How do I get an FTP directory listing?
5.16 I want a different time-out
5.17 Can I write a server with libcurl?
5.18 Does libcurl use threads?
6. License Issues
6.1 I have a GPL program, can I use the libcurl library?
6.2 I have a closed-source program, can I use the libcurl library?
6.3 I have a BSD licensed program, can I use the libcurl library?
6.4 I have a program that uses LGPL libraries, can I use libcurl?
6.5 Can I modify curl/libcurl for my program and keep the changes secret?
6.6 Can you please change the curl/libcurl license to XXXX?
6.7 What are my obligations when using libcurl in my commercial apps?
7. PHP/CURL Issues
7.1 What is PHP/CURL?
7.2 Who wrote PHP/CURL?
7.3 Can I perform multiple requests using the same handle?
7.4 Does PHP/CURL have dependencies?
8. Development
8.1 Why does curl use C89?
8.2 Will curl be rewritten?
==============================================================================
1. Philosophy
1.1 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, POP3, POP3S,
RTMP, RTMPS, 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, including Solaris, NetBSD, FreeBSD, OpenBSD, Darwin, HP-UX,
IRIX, AIX, Tru64, Linux, UnixWare, HURD, Windows, Amiga, OS/2, macOS,
Ultrix, QNX, OpenVMS, RISC OS, Novell NetWare, DOS, Symbian, OSF, Android,
Minix, IBM TPF and more...
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 to help you:
https://media.merriam-webster.com/soundc11/c/curl0001.wav
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.)
1.2 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.
1.3 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.
1.4 When will you make curl do XXXX ?
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
magic with the supported protocols than curl currently does, chances are
good we will 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. Simply go to the GitHub repository which resides at
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 will get into curl faster.
1.5 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 file.
curl is developed by a community, with Daniel at the wheel.
1.6 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 and other services like the bug
tracker at https://github.com/curl/curl. Also again, some companies have
sponsored certain parts of the development in the past and I hope some will
continue to do so in the future.
If you want to support our project, consider a donation or a banner-program
or even better: by helping us with coding, documenting or testing etc.
See also: https://curl.se/sponsors.html
1.7 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 will be living in parallel with curl.com and wish them
every success.
1.8 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 in the MANUAL document and online at
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 simply suspect a security problem in curl or libcurl,
submit all the details at https://hackerone.one/curl. On there 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 taking to the curl security team by emailing
security at curl.se (closed list of receivers, mails are not disclosed).
1.9 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 on the curl website:
https://curl.se/support.html
1.10 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 2020, we estimate that curl runs in roughly ten billion installations
world wide.
1.11 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 that you extract the collection yourself from Mozilla
Firefox (by running 'make ca-bundle), or by using our online service setup
for this purpose: https://curl.se/docs/caextract.html
1.12 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.
1.13 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 gives a good explanation of ECCNs at
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.doc.gov/licensing/exportingbasics.htm
https://www.bis.doc.gov/licensing/do_i_needaneccn.html
An incomprehensible description of the two numbers above is here
https://www.bis.doc.gov/index.php/documents/new-encryption/1653-ccl5-pt2-3
1.14 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 for any reason cannot or will not deal 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.
Lots of more details are found in the CONTRIBUTE.md and INTERNALS.md
documents.
1.15 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
2. Install Related Problems
2.1 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 is 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.
2.2 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: OpenSSL,
LibreSSL, BoringSSL, AWS-LC, GnuTLS, wolfSSL, mbedTLS, Secure Transport
(native iOS/macOS), Schannel (native Windows), BearSSL or Rustls. They all
have their pros and cons, and we try to maintain a comparison of them here:
https://curl.se/docs/ssl-compared.html
2.3 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 https://curl.se/windows,
then Windows Update will cease 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
from https://curl.se/windows into a separate location.
2.4 Does curl support SOCKS (RFC 1928) ?
Yes, SOCKS 4 and 5 are supported.
3. Usage problems
3.1 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 simply 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.
Also, check out the other paragraph in this FAQ labeled "configure does not
find OpenSSL even when it is installed".
3.2 How do I tell curl to resume a transfer?
curl supports resumed transfers both ways on both FTP and HTTP.
Try the -C option.
3.3 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 will
receive 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 and TheArtOfHttpScripting
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.
3.4 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.
3.5 How can I disable the Accept: */* header?
You can change 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.
3.6 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 item 3.14 regarding JavaScript.
3.7 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"
3.8 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 http://example.com
Not all redirects are HTTP ones, see 4.14
3.9 How do I use curl in my favorite programming language?
Many programming languages have interfaces/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 2021, there were interfaces available for the following
languages: Ada95, Basic, C, C++, Ch, Cocoa, D, Delphi, Dylan, Eiffel,
Euphoria, Falcon, Ferite, Gambas, glib/GTK+, Go, Guile, Harbour, Haskell,
Java, Julia, Lisp, Lua, Mono, .NET, node.js, Object-Pascal, OCaml, Pascal,
Perl, PHP, PostgreSQL, Python, R, Rexx, Ring, RPG, Ruby, Rust, Scheme,
Scilab, S-Lang, Smalltalk, SP-Forth, SPL, Tcl, Visual Basic, Visual FoxPro,
Q, wxwidgets, XBLite and Xoho. By the time you read this, additional ones
may have appeared.
3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP?
curl adheres to the HTTP spec, which basically 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 is of course just as good and you would just use the proper
library options to do the same.
3.11 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]
3.12 Why do FTP-specific features over HTTP proxy fail?
Because when you use an HTTP proxy, the protocol spoken on the network will
be 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).
3.13 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 will 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.
3.14 Does curl support JavaScript or PAC (automated proxy config)?
Many webpages do magic stuff using embedded JavaScript. curl and libcurl
have no built-in support for that, so it will be treated just 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
just 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.
3.15 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 wrapper scripts with that functionality (for example the
curlmirror perl script), and you can write programs based on libcurl to do
it, but the command line tool curl itself cannot.
3.16 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 pass phrase 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.
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.
The server certificate verification process is made by using a Certificate
Authority certificate ("CA cert") that was used to sign the server
certificate. Server certificate verification is enabled by default in curl
and libcurl and is often the reason for problems as explained in FAQ entry
4.12 and the SSLCERTS document
(https://curl.se/docs/sslcerts.html). 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 need to explicitly disable the verification to
connect to the server.
3.17 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/
or the not-quite-kosher-but-more-readable way, by simply starting the path
section of the URL with a slash:
curl ftp://ftp.example.com//tmp/
3.18 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.
3.19 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" http://127.0.0.1/
You can also opt to add faked hostname entries to curl with the --resolve
option. That has the added benefit that things like redirects will also work
properly. The above operation would instead be done as:
curl --resolve www.example.com:80:127.0.0.1 http://www.example.com/
3.20 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 just a different protocol prefix:
curl -O -u user:password scp://example.com/~/file.txt
3.21 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 will also occur if you pass a wrongly spelled protocol
part as in "htpt://example.com" or as in the less evident case if you prefix
the protocol part with a space as in " http://example.com/".
3.22 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 just pass in a URL like
"curl http://example.com" it will use GET. If you use -d or -F curl will use
POST, -I will cause a HEAD and -T will make 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 will effectively prevent curl from behaving
correctly. Be aware.
4. Running Problems
4.2 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 'http://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).
4.3 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'
4.4 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" will be returned. That is simply 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.
4.5 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:
4.5.1 "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.
4.5.2 "401 Unauthorized"
The request requires user authentication.
4.5.3 "403 Forbidden"
The server understood the request, but is refusing to fulfill it.
Authorization will not help and the request SHOULD NOT be repeated.
4.5.4 "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.
4.5.5 "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.
4.5.6 "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="http://same_url_now_with_a_trailing_slash/">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.
4.6 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.
4.7 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 will also
attempt 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.
4.8 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.
4.9 curl cannot authenticate to a server that requires NTLM?
NTLM support requires OpenSSL, GnuTLS, mbedTLS, Secure Transport, or
Microsoft Windows libraries at build-time to provide this functionality.
4.10 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.
4.11 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.
4.12 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 CA's 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 server misconfiguration. A
good way to figure out if this is the case it to use the SSL Labs server
test and check the certificate chain: https://www.ssllabs.com/ssltest/
Details are also in the SSLCERTS.md document, found online here:
https://curl.se/docs/sslcerts.html
4.13 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://www.codeproject.com/Articles/1144/Beating-the-Daylight-Savings-Time-bug-and-getting
4.14 Redirects work in browser but not with curl
curl supports HTTP redirects well (see item 3.8). Browsers generally support
at least two other ways to perform redirects that curl does not:
Meta tags. You can write an HTML tag that will cause 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.
4.15 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 will therefore immediately connect and try 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 will then of course use the
standard FTP port 21 by default.
4.16 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.
However, many servers do not implement the Expect: stuff properly and if the
server does not respond (positively) within 1 second libcurl will continue
and send 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.
4.17 Non-functional connect timeouts
In most Windows setups having a timeout longer than 21 seconds make no
difference, as it will only send 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 option TcpMaxConnectRetransmissions on this page:
https://support.microsoft.com/en-us/kb/175523/en-us
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 will make (lib)curl to consider the connection connected
and thus the connect timeout will not trigger.
4.18 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 will find that even if D:\blah.txt does exist, curl returns a 'file
not found' error.
According to RFC 1738 (https://www.ietf.org/rfc/rfc1738.txt),
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 will resolve to 'C:\blah.txt',
and if that does not exist you will 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.
4.19 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, just possibly
delayed. Eventually, the physical break will be fixed or the data will be
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 will 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 will abort 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 (see also item 5.13).
4.20 curl does not return error for HTTP non-200 responses
Correct. Unless you use -f (--fail).
When doing HTTP transfers, curl will perform exactly what you are asking it
to do and if successful it will 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 simply 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.
5. libcurl Issues
5.1 Is libcurl thread-safe?
Yes.
We have written the libcurl code specifically adjusted for multi-threaded
programs. libcurl will use 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 to learn more:
https://curl.se/libcurl/c/threadsafe.html
5.2 How can I receive all data into a large memory chunk?
[ See also the examples/getinmemory.c source ]
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 will be passed to the callback
instead of a FILE * to a file:
/* imaginary 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 = (char *)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;
}
5.3 How do I fetch multiple files with libcurl?
libcurl has excellent support for transferring multiple files. You should
just 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
will enable libcurl to use persistent connections.
5.4 Does libcurl do Winsock initialization on Win32 systems?
Yes, if told to in the curl_global_init() call.
5.5 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 that simply writes the data to the specified FILE *.
Similarly, if you use CURLOPT_READDATA you must also specify
CURLOPT_READFUNCTION.
5.6 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 will attempt to reuse
connections for all URLs specified on the same command line/config file, and
libcurl will reuse 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 will be
kept within the multi handle and will be shared among all the easy handles
that are used within the same multi handle.
5.7 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 will look 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 libcurl*.dll.
-----------------------------------------------------------
MinGW: libcurl.a libcurldll.a
MSVC (release): libcurl.lib libcurl_imp.lib
MSVC (debug): libcurld.lib libcurld_imp.lib
Borland: libcurl.lib libcurl_imp.lib
5.8 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' will tell you more details
5.9 How does libcurl resolve hostnames?
libcurl supports a large number of name resolve functions. One of them is
picked at build-time and will be 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 that can use one of four different hostname resolve
calls (depending on what your system supports):
A - gethostbyname()
B - gethostbyname_r() with 3 arguments
C - gethostbyname_r() with 5 arguments
D - gethostbyname_r() with 6 arguments
- The IPv6-resolver that uses getaddrinfo()
- The c-ares based name resolver that uses the c-ares library for resolves.
Using this offers asynchronous name resolves.
- The threaded resolver (default option on Windows). It uses:
A - gethostbyname() on plain IPv4 hosts
B - getaddrinfo() on IPv6 enabled hosts
Also note that libcurl never resolves or reverse-lookups addresses given as
pure numbers, such as 127.0.0.1 or ::1.
5.10 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.
5.11 How do I make libcurl not receive the whole HTTP response?
You make the write callback (or progress callback) return an error and
libcurl will then abort the transfer.
5.12 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 will 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 will see you coming from. You may also consider using
https://www.torproject.org/ .
5.13 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 will stop it immediately.
Instead, you need to make sure that one of the callbacks you use returns an
appropriate value that will stop 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.
5.14 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:
// f is the pointer to your object.
static size_t YourClass::func(void *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);
5.15 How do I get an FTP directory listing?
If you end the FTP URL you request with a slash, libcurl will provide 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
will return 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 in libcurl one such existing
list parser is available at https://cr.yp.to/ftpparse.html Versions of
libcurl since 7.21.0 also provide the ability to specify a wildcard to
download multiple files from one FTP directory.
5.16 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.
5.17 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.
5.18 Does libcurl use threads?
Put simply: no, libcurl will execute in the same thread you call it in. All
callbacks will be 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 will do transfers
asynchronously - still in the same single thread.
libcurl will potentially internally use threads for name resolving, if it
was built to work like that, but in those cases it will create the child
threads by itself and they will only be used and then killed internally by
libcurl and never exposed to the outside.
6. License Issues
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
just a brief summary for the cases we get the most questions. (Parts of this
section was much enhanced by Bjorn Reese.)
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.
6.1 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.
6.2 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.
6.3 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.
6.4 I have a program that uses LGPL libraries, can I use libcurl?
Yes
The LGPL license does not clash with other licenses.
6.5 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.
6.6 Can you please change the curl/libcurl license to XXXX?
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.
6.7 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 basically 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.
7. PHP/CURL Issues
7.1 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.
7.2 Who wrote PHP/CURL?
PHP/CURL was initially written by Sterling Hughes.
7.3 Can I perform multiple requests using the same handle?
Yes - at least in PHP version 4.3.8 and later (this has been known to not
work in earlier versions, but the exact version when it started to work is
unknown to me).
After a transfer, you just set new options in the handle and make another
transfer. This will make libcurl reuse the same connection if it can.
7.4 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.
8. Development
8.1 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 will 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 will offer us
enough of a benefit to warrant the risk of cutting off a share of users.
8.2 Will curl be rewritten?
In one go: no. Little by little over time? Maybe.
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 will 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/CHANGES.md 0000644 00000000666 15116230442 0013233 0 ustar 00 <!--
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
-->
In a release tarball, check the RELEASES-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/BUGS.md 0000644 00000027246 15116230450 0012725 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 on the [curl security tracker at
HackerOne](https://hackerone.com/curl).
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 use 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 actually just 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 just lump over something to us and it then
magically 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, but
instead, they "just want the bug fixed". That is fine, just 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/doc/alt-curlssl11/TODO 0000644 00000141660 15116230455 0012335 0 ustar 00 _ _ ____ _
___| | | | _ \| |
/ __| | | | |_) | |
| (__| |_| | _ <| |___
\___|\___/|_| \_\_____|
Things that could be nice to do in the future
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 are subject for fixing.
1. libcurl
1.1 TFO support on Windows
1.2 Consult %APPDATA% also for .netrc
1.3 struct lifreq
1.4 alt-svc sharing
1.5 get rid of PATH_MAX
1.6 thread-safe sharing
1.8 CURLOPT_RESOLVE for any port number
1.9 Cache negative name resolves
1.10 auto-detect proxy
1.11 minimize dependencies with dynamically loaded modules
1.12 updated DNS server while running
1.13 c-ares and CURLOPT_OPENSOCKETFUNCTION
1.14 connect to multiple IPs in parallel
1.15 Monitor connections in the connection pool
1.16 Try to URL encode given URL
1.17 Add support for IRIs
1.18 try next proxy if one does not work
1.19 provide timing info for each redirect
1.20 SRV and URI DNS records
1.21 netrc caching and sharing
1.22 CURLINFO_PAUSE_STATE
1.23 Offer API to flush the connection pool
1.25 Expose tried IP addresses that failed
1.28 FD_CLOEXEC
1.29 WebSocket read callback
1.30 config file parsing
1.31 erase secrets from heap/stack after use
1.32 add asynch getaddrinfo support
1.33 make DoH inherit more transfer properties
2. libcurl - multi interface
2.1 More non-blocking
2.2 Better support for same name resolves
2.3 Non-blocking curl_multi_remove_handle()
2.4 Split connect and authentication process
2.5 Edge-triggered sockets should work
2.6 multi upkeep
2.7 Virtual external sockets
2.8 dynamically decide to use socketpair
3. Documentation
3.1 Improve documentation about fork safety
4. FTP
4.1 HOST
4.4 Support CURLOPT_PREQUOTE for directories listings
4.6 GSSAPI via Windows SSPI
4.7 STAT for LIST without data connection
4.8 Passive transfer could try other IP addresses
5. HTTP
5.1 Provide the error body from a CONNECT response
5.2 Obey Retry-After in redirects
5.3 Rearrange request header order
5.4 Allow SAN names in HTTP/2 server push
5.5 auth= in URLs
5.6 alt-svc should fallback if alt-svc does not work
5.7 Require HTTP version X or higher
6. TELNET
6.1 ditch stdin
6.2 ditch telnet-specific select
6.3 feature negotiation debug data
6.4 exit immediately upon connection if stdin is /dev/null
7. SMTP
7.1 Passing NOTIFY option to CURLOPT_MAIL_RCPT
7.2 Enhanced capability support
7.3 Add CURLOPT_MAIL_CLIENT option
8. POP3
8.2 Enhanced capability support
9. IMAP
9.1 Enhanced capability support
10. LDAP
10.1 SASL based authentication mechanisms
10.2 CURLOPT_SSL_CTX_FUNCTION for LDAPS
10.3 Paged searches on LDAP server
10.4 Certificate-Based Authentication
11. SMB
11.1 File listing support
11.2 Honor file timestamps
11.3 Use NTLMv2
11.4 Create remote directories
12. FILE
12.1 Directory listing on non-POSIX
13. TLS
13.1 TLS-PSK with OpenSSL
13.2 TLS channel binding
13.3 Defeat TLS fingerprinting
13.4 Consider OCSP stapling by default
13.5 Export session ids
13.6 Provide callback for cert verification
13.7 Less memory massaging with Schannel
13.8 Support DANE
13.9 TLS record padding
13.10 Support Authority Information Access certificate extension (AIA)
13.11 Some TLS options are not offered for HTTPS proxies
13.13 Make sure we forbid TLS 1.3 post-handshake authentication
13.14 Support the clienthello extension
13.16 Share the CA cache
13.17 Add missing features to TLS backends
14. Proxy
14.1 Retry SOCKS handshake on address type not supported
15. Schannel
15.1 Extend support for client certificate authentication
15.2 Extend support for the --ciphers option
15.4 Add option to allow abrupt server closure
16. SASL
16.1 Other authentication mechanisms
16.2 Add QOP support to GSSAPI authentication
17. SSH protocols
17.1 Multiplexing
17.2 Handle growing SFTP files
17.3 Read keys from ~/.ssh/id_ecdsa, id_ed25519
17.4 Support CURLOPT_PREQUOTE
17.5 SSH over HTTPS proxy with more backends
17.6 SFTP with SCP://
18. Command line tool
18.1 sync
18.2 glob posts
18.4 --proxycommand
18.5 UTF-8 filenames in Content-Disposition
18.6 Option to make -Z merge lined based outputs on stdout
18.7 specify which response codes that make -f/--fail return error
18.9 Choose the name of file in braces for complex URLs
18.10 improve how curl works in a Windows console window
18.11 Windows: set attribute 'archive' for completed downloads
18.12 keep running, read instructions from pipe/socket
18.13 Acknowledge Ratelimit headers
18.14 --dry-run
18.15 --retry should resume
18.17 consider filename from the redirected URL with -O ?
18.18 retry on network is unreachable
18.19 expand ~/ in config files
18.20 hostname sections in config files
18.21 retry on the redirected-to URL
18.23 Set the modification date on an uploaded file
18.24 Use multiple parallel transfers for a single download
18.25 Prevent terminal injection when writing to terminal
18.26 Custom progress meter update interval
18.27 -J and -O with %-encoded filenames
18.28 -J with -C -
18.29 --retry and transfer timeouts
19. Build
19.2 Enable PIE and RELRO by default
19.3 Do not use GNU libtool on OpenBSD
19.4 Package curl for Windows in a signed installer
19.5 make configure use --cache-file more and better
20. Test suite
20.1 SSL tunnel
20.2 more protocols supported
20.3 more platforms supported
20.4 write an SMB test server to replace impacket
20.5 Use the RFC 6265 test suite
20.6 Run web-platform-tests URL tests
21. MQTT
21.1 Support rate-limiting
21.2 Support MQTTS
21.3 Handle network blocks
22. TFTP
22.1 TFTP does not convert LF to CRLF for mode=netascii
23. Gopher
23.1 Handle network blocks
==============================================================================
1. libcurl
1.1 TFO support on Windows
libcurl supports the CURLOPT_TCP_FASTOPEN option since 7.49.0 for Linux and
macOS. Windows supports TCP Fast Open starting with Windows 10, version 1607
and we should add support for it.
TCP Fast Open is supported on several platforms but not on Windows. Work on
this was once started but never finished.
See https://github.com/curl/curl/pull/3378
1.2 Consult %APPDATA% also for .netrc
%APPDATA%\.netrc is not considered when running on Windows. should not it?
See https://github.com/curl/curl/issues/4016
1.3 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.
1.4 alt-svc sharing
The share interface could benefit from allowing the alt-svc cache to be
possible to share between easy handles.
See 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 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.
1.5 get rid of PATH_MAX
Having code use and rely on PATH_MAX is not nice:
https://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
Currently the libssh2 SSH based code uses it, but to remove PATH_MAX from
there we need libssh2 to properly tell us when we pass in a too small buffer
and its current API (as of libssh2 1.2.7) does not.
1.6 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.
1.8 CURLOPT_RESOLVE for any port number
This option allows applications to set a replacement IP address for a given
host + port pair. Consider making support for providing a replacement address
for the hostname on all port numbers.
See https://github.com/curl/curl/issues/1264
1.9 Cache negative name resolves
A name resolve that has failed is likely to fail when made again within a
short period of time. Currently we only cache positive responses.
1.10 auto-detect proxy
libcurl could be made to detect the system proxy setup automatically and use
that. On Windows, macOS and Linux desktops for example.
The pull-request to use libproxy for this was deferred due to doubts on the
reliability of the dependency and how to use it:
https://github.com/curl/curl/pull/977
libdetectproxy is a (C++) library for detecting the proxy on Windows
https://github.com/paulharris/libdetectproxy
1.11 minimize dependencies with dynamically loaded modules
We can create a system with loadable modules/plug-ins, where these modules
would be the ones that link to 3rd party libs. That would allow us to avoid
having to load ALL dependencies since only the necessary ones for this
app/invoke/used protocols would be necessary to load. See
https://github.com/curl/curl/issues/349
1.12 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.
https://github.com/curl/curl/issues/2251
1.13 c-ares and CURLOPT_OPENSOCKETFUNCTION
curl creates most sockets via the CURLOPT_OPENSOCKETFUNCTION callback and
close them with the CURLOPT_CLOSESOCKETFUNCTION callback. However, 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 https://github.com/curl/curl/issues/2734
1.14 connect to multiple IPs in parallel
curl currently implements the happy eyeball algorithm for connecting to the
IPv4 and IPv6 alternatives for a host in parallel, sticking with the
connection that "wins". We could implement a similar algorithm per individual
IP family as well when there are multiple available addresses: start with the
first address, then start a second attempt N milliseconds after and then a
third another N milliseconds later. That way there would be less waiting when
the first IP has problems. It also improves the connection timeout value
handling for multiple address situations.
1.15 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.
1.16 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 (basically do what the redirect
following code already does).
https://github.com/curl/curl/issues/514
1.17 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.
1.18 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 PACs.
https://github.com/curl/curl/issues/896
1.19 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.
https://github.com/curl/curl/issues/6743
1.20 SRV and URI DNS records
Offer support for resolving SRV and URI DNS records for libcurl to know which
server to connect to for various protocols (including HTTP).
1.21 netrc caching and sharing
The netrc file is read and parsed each time a connection is setup, which
means that if a transfer needs multiple connections for authentication or
redirects, the file might be reread (and parsed) multiple times. This makes
it impossible to provide the file as a pipe.
1.22 CURLINFO_PAUSE_STATE
Return information about the transfer's current pause state, in both
directions. https://github.com/curl/curl/issues/2588
1.23 Offer API to flush the connection pool
Sometimes applications want to flush all the existing connections kept alive.
An API could allow a forced flush or just a forced loop that would properly
close all connections that have been closed by the server already.
1.25 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 + dest IP, source + dest port
and protocol (UDP or TCP) for each failure. Possibly as a callback. Perhaps
also provide "reason".
https://github.com/curl/curl/issues/2126
1.28 FD_CLOEXEC
It sets the close-on-exec flag for the file descriptor, which causes the file
descriptor to be automatically (and atomically) closed when any of the
exec-family functions succeed. Should probably be set by default?
https://github.com/curl/curl/issues/2252
1.29 WebSocket read callback
Call the read callback once the connection is established to allow sending
the first message in the connection.
https://github.com/curl/curl/issues/11402
1.30 config file parsing
Consider providing an API, possibly in a separate companion library, for
parsing a config file like curl's -K/--config option to allow applications to
get the same ability to read curl options from files.
See https://github.com/curl/curl/issues/3698
1.31 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...
https://github.com/curl/curl/issues/7268
1.32 add asynch getaddrinfo support
Use getaddrinfo_a() to provide an asynch name resolver backend to libcurl
that does not use threads and does not depend on c-ares. The getaddrinfo_a
function is (probably?) glibc specific but that is a widely used libc among
our users.
https://github.com/curl/curl/pull/6746
1.33 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 (ie 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 https://github.com/curl/curl/issues/6605
2. libcurl - multi interface
2.1 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:
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. See section 2.3.
- Calling curl_ws_send() from a callback
2.2 Better support for same name resolves
If a name resolve has been initiated for name NN and a second easy handle
wants to resolve that 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 host
name when the DNS resolver can get flooded.
2.3 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.
2.4 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.
2.5 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().
2.6 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 https://github.com/curl/curl/issues/3199
2.7 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 https://github.com/curl/curl/issues/5835
2.8 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 https://github.com/curl/curl/issues/4829
3. Documentation
3.1 Improve documentation about fork safety
See https://github.com/curl/curl/issues/6968
4. FTP
4.1 HOST
HOST is a command for a client to tell which hostname to use, to offer FTP
servers named-based virtual hosting:
https://datatracker.ietf.org/doc/html/rfc7151
4.4 Support CURLOPT_PREQUOTE for directions listings
The lack of support is mostly an oversight and requires the FTP state machine
to get updated to get fixed.
https://github.com/curl/curl/issues/8602
4.6 GSSAPI via Windows SSPI
In addition to currently supporting the SASL GSSAPI mechanism (Kerberos V5)
via third-party GSS-API libraries, such as Heimdal or MIT Kerberos, also add
support for GSSAPI authentication via Windows SSPI.
4.7 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 usedw data connection: https://www.nsftools.com/tips/RawFTP.htm#STAT
This is not detailed in any FTP specification.
4.8 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 https://github.com/curl/curl/issues/1508
5. HTTP
5.1 Provide the error body from a CONNECT response
When curl receives a body response from a CONNECT request to a proxy, it
always just 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 https://github.com/curl/curl/issues/9513
5.2 Obey Retry-After in redirects
The Retry-After is said to dicate "the minimum time that the user agent is
asked to wait before issuing the redirected request" and libcurl does not
obey this.
See https://github.com/curl/curl/issues/11447
5.3 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.
5.4 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 https://github.com/curl/curl/pull/3581
5.5 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.
5.6 alt-svc should fallback if alt-svc does not work
The alt-svc: header provides a set of alternative services for curl to use
instead of the original. If the first attempted one fails, it should try the
next etc and if all alternatives fail go back to the original.
See https://github.com/curl/curl/issues/4908
5.7 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 https://github.com/curl/curl/issues/7980
6. TELNET
6.1 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.
6.2 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.
6.3 feature negotiation debug data
Add telnet feature negotiation data to the debug callback as header data.
6.4 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
7. SMTP
7.1 Passing 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" );
https://github.com/curl/curl/issues/8232
7.2 Enhanced capability support
Add the ability, for an application that uses libcurl, to obtain the list of
capabilities returned from the EHLO command.
7.3 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
8. POP3
8.2 Enhanced capability support
Add the ability, for an application that uses libcurl, to obtain the list of
capabilities returned from the CAPA command.
9. IMAP
9.1 Enhanced capability support
Add the ability, for an application that uses libcurl, to obtain the list of
capabilities returned from the CAPABILITY command.
10. LDAP
10.1 SASL based authentication mechanisms
Currently the LDAP module only supports ldap_simple_bind_s() in order to bind
to an LDAP server. However, this function sends username and password details
using the simple authentication mechanism (as clear text). However, it should
be possible to use ldap_bind_s() instead specifying the security context
information ourselves.
10.2 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.
https://github.com/curl/curl/issues/4108
10.3 Paged searches on LDAP server
https://github.com/curl/curl/issues/4452
10.4 Certificate-Based Authentication
LDAPS not possible with macOS and Windows with Certificate-Based Authentication
https://github.com/curl/curl/issues/9641
11. SMB
11.1 File listing support
Add support for listing the contents of an SMB share. The output should
probably be the same as/similar to FTP.
11.2 Honor file timestamps
The timestamp of the transferred file should reflect that of the original
file.
11.3 Use NTLMv2
Currently the SMB authentication uses NTLMv1.
11.4 Create remote directories
Support for creating remote directories when uploading a file to a directory
that does not exist on the server, just like --ftp-create-dirs.
12. FILE
12.1 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.
13. TLS
13.1 TLS-PSK with OpenSSL
Transport Layer Security pre-shared key ciphersuites (TLS-PSK) is a set of
cryptographic protocols that provide secure communication based on pre-shared
keys (PSKs). These pre-shared keys are symmetric keys shared in advance among
the communicating parties.
https://github.com/curl/curl/issues/5081
13.2 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
https://github.com/curl/curl/issues/9226
13.3 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.
13.4 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.
https://github.com/curl/curl/issues/15483
13.5 Export session ids
Add an interface to libcurl that enables "session IDs" to get
exported/imported. Cris Bailiff said: "OpenSSL has functions which can
serialise the current SSL state to a buffer of your choice, and recover/reset
the state from such a buffer at a later date - this is used by mod_ssl for
apache to implement and SSL session ID cache".
13.6 Provide callback for cert verification
OpenSSL supports a callback for customised 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.
13.7 Less memory massaging with Schannel
The Schannel backend does a lot of custom memory management we would rather
avoid: the repeated alloc + 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.
13.8 Support DANE
DNS-Based Authentication of Named Entities (DANE) is a way to provide SSL
keys and certs over DNS using DNSSEC as an alternative to the CA model.
https://www.rfc-editor.org/rfc/rfc6698.txt
An initial patch was posted by Suresh Krishnaswamy on March 7th 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 . libunbound may be the
correct library to base this development on.
Björn Stenberg wrote a separate initial take on DANE that was never
completed.
13.9 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 https://github.com/curl/curl/issues/5398
13.10 Support Authority Information Access certificate extension (AIA)
AIA can provide various things like CRLs 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.
See https://github.com/curl/curl/issues/2793
13.11 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
https://github.com/curl/curl/issues/12286
13.13 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 https://github.com/curl/curl/issues/5396
13.14 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
https://github.com/curl/curl/issues/2299
13.16 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.
13.17 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.
14. Proxy
14.1 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 https://github.com/curl/curl/issues/17222
15. Schannel
15.1 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://msdn.microsoft.com/en-us/library/windows/desktop/aa375447.aspx
15.2 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://msdn.microsoft.com/en-us/library/windows/desktop/aa380161.aspx
15.4 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.
https://github.com/curl/curl/issues/4427
16. SASL
16.1 Other authentication mechanisms
Add support for other authentication mechanisms such as OLP,
GSS-SPNEGO and others.
16.2 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).
17. SSH protocols
17.1 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.
17.2 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 just
attempt to download more to see if there is more to get...
https://github.com/curl/curl/issues/4344
17.3 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.
https://github.com/curl/curl/issues/8586
17.4 Support CURLOPT_PREQUOTE
The two other QUOTE options are supported for SFTP, but this was left out for
unknown reasons.
17.5 SSH over HTTPS proxy with more backends
The SSH based protocols SFTP and SCP did not work over HTTPS proxy at
all until PR https://github.com/curl/curl/pull/6021 brought the
functionality with the libssh2 backend. Presumably, this support
can/could be added for the other backends as well.
17.6 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.
18. Command line tool
18.1 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.
18.2 glob posts
Globbing support for -d and -F, as in 'curl -d "name=foo[0-9]" URL'.
This is easily scripted though.
18.4 --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 https://github.com/curl/curl/issues/4941
18.5 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.
https://github.com/curl/curl/issues/1888
18.6 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.
https://github.com/curl/curl/issues/5175
18.7 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
18.9 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 https://github.com/curl/curl/issues/221
18.10 improve how curl works in a Windows console window
If you pull the scrollbar when transferring with curl in a Windows console
window, the transfer is interrupted and can get disconnected. This can
probably be improved. See https://github.com/curl/curl/issues/322
18.11 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 https://github.com/curl/curl/issues/3354
18.12 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.
18.13 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/draft-ietf-httpapi-ratelimit-headers/
See https://github.com/curl/curl/issues/5406
18.14 --dry-run
A command line option that makes curl show exactly what it would do and send
if it would run for real.
See https://github.com/curl/curl/issues/5426
18.15 --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 https://github.com/curl/curl/issues/1084
18.17 consider filename from the redirected URL with -O ?
When a user gives a URL and uses -O, and curl follows a redirect to a new
URL, the filename is not extracted and used from the newly redirected-to URL
even if the new URL may have a much more sensible filename.
This is clearly documented and helps for security since there is no surprise
to users which filename that might get overwritten, but maybe a new option
could allow for this or maybe -J should imply such a treatment as well as -J
already allows for the server to decide what filename to use so it already
provides the "may overwrite any file" risk.
This is extra tricky if the original URL has no filename part at all since
then the current code path does error out with an error message, and we
cannot *know* already at that point if curl is redirected to a URL that has a
filename...
See https://github.com/curl/curl/issues/1241
18.18 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?
https://github.com/curl/curl/issues/1603
18.19 expand ~/ in config files
For example .curlrc could benefit from being able to do this.
See https://github.com/curl/curl/issues/2317
18.20 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.
18.21 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 https://github.com/curl/curl/issues/5462
18.23 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 https://github.com/curl/curl/issues/5768
18.24 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 https://github.com/curl/curl/issues/5774
18.25 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 https://github.com/curl/curl/issues/6150
18.26 Custom progress meter update interval
Users who are for example doing large downloads in CI or remote setups might
want the occasional progress meter update to see that the transfer is
progressing and has not stuck, but they may not appreciate the
many-times-a-second frequency curl can end up doing it with now.
18.27 -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 basically 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.
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.
18.28 -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
18.29 --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 and Mandriva bug report
https://qa.mandriva.com/show_bug.cgi?id=22565
19. Build
19.2 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.
19.3 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
magic to detect if this system is an OpenBSD host and then use the OpenBSD
libtool instead.
See https://github.com/curl/curl/issues/5862
19.4 Package curl for Windows in a signed installer
See https://github.com/curl/curl/issues/5424
19.5 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 https://github.com/curl/curl/issues/7753
20. Test suite
20.1 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
20.2 more protocols supported
Extend the test suite to include more protocols. The telnet could just do FTP
or http operations (for which we have test servers).
20.3 more platforms supported
Make the test suite work on more platforms. OpenBSD and macOS. Remove
fork()s and it should become even more portable.
20.4 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 https://github.com/curl/curl/issues/15697
20.5 Use the RFC 6265 test suite
A test suite made for HTTP cookies (RFC 6265) by Adam Barth is available at
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 deviances. Ideally, that would even be
incorporated into our regular test suite.
20.6 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 https://github.com/curl/curl/issues/4477
21. MQTT
21.1 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.
21.2 Support MQTTS
21.3 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.
22. TFTP
22.1 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 https://github.com/curl/curl/issues/12655
23. Gopher
23.1 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/FEATURES.md 0000644 00000014023 15116230462 0013373 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/COPYING 0000644 00000002100 15116230467 0012664 0 ustar 00 COPYRIGHT AND PERMISSION NOTICE
Copyright (c) 1996 - 2025, 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/TheArtOfHttpScripting.md 0000644 00000067723 15116230475 0016377 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 http://www.example.com/
## See the Timing
Many times you may wonder what exactly is taking all the time, or you just
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 http://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 http://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 http://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 http://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 http://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 http://user:password@example.org/
or
curl -u user:password http://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 just 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 just 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 http://url1.example.com http://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 http://url1.example.com http://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 basically 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 http://example.com --next http://example.com
To first send a POST and then a GET:
curl -d score=10 http://example.com/post.cgi --next http://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 just 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, just enter the expected created
URL:
curl "http://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>
```
And 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" http://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" http://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 just 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 http://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 name:password http://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 http://www.example.come http://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 simply 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 http://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 just 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" http://www.example.com
Cookies are sent as common HTTP headers. This is practical as it allows curl
to record cookies simply 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 http://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 http://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 http://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 \
http://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, simply 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:" http://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: http://nowhere" http://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
simply adding `-X POST` in a command line like:
curl -X POST http://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 just 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/README 0000644 00000003200 15116230502 0012501 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 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.git
(you will get a directory named curl created, filled with the source code)
SECURITY PROBLEMS
Report suspected security problems via our HackerOne page and not in public.
https://hackerone.com/curl
NOTICE
Curl contains pieces of source code that is Copyright (c) 1998, 1999
Kungliga Tekniska Högskolan. This notice is included here to comply with the
distribution terms.
usr/lib64/libcurl.so.4.8.0 0000755 00003436660 15116230507 0010767 0 ustar 00 ELF >