curl.1: detail how short/long options work

[platform/upstream/curl.git] / docs / curl.1

.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2013, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
.\" * are also available at http://curl.haxx.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" **************************************************************************
.\"
.TH curl 1 "27 July 2012" "Curl 7.27.0" "Curl Manual"
.SH NAME
curl \- transfer a URL
.SH SYNOPSIS
.B curl [options]
.I [URL...]
.SH DESCRIPTION
.B curl
is a tool to transfer data from or to a server, using one of the supported
protocols (DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP,
LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMTP, SMTPS, TELNET and TFTP).  The
command is designed to work without user interaction.

curl offers a busload of useful tricks like proxy support, user
authentication, FTP upload, HTTP post, SSL connections, cookies, file transfer
resume, Metalink, and more. As you will see below, the number of features will
make your head spin!

curl is powered by libcurl for all transfer-related features. See
.BR libcurl (3)
for details.
.SH URL
The URL syntax is protocol-dependent. You'll find a detailed description in
RFC 3986.

You can specify multiple URLs or parts of URLs by writing part sets within
braces as in:

 http://site.{one,two,three}.com

or you can get sequences of alphanumeric series by using [] as in:

 ftp://ftp.numericals.com/file[1-100].txt
 ftp://ftp.numericals.com/file[001-100].txt    (with leading zeros)
 ftp://ftp.letters.com/file[a-z].txt

Nested sequences are not supported, but you can use several ones next to each
other:

 http://any.org/archive[1996-1999]/vol[1-4]/part{a,b,c}.html

You can specify any amount of URLs on the command line. They will be fetched
in a sequential manner in the specified order.

You can specify a step counter for the ranges to get every Nth number or
letter:

 http://www.numericals.com/file[1-100:10].txt
 http://www.letters.com/file[a-z:2].txt

If you specify URL without protocol:// prefix, curl will attempt to guess what
protocol you might want. It will then default to HTTP but try other protocols
based on often-used host name prefixes. For example, for host names starting
with "ftp." curl will assume you want to speak FTP.

curl will do its best to use what you pass to it as a URL. It is not trying to
validate it as a syntactically correct URL by any means but is instead
\fBvery\fP liberal with what it accepts.

curl will attempt to re-use connections for multiple file transfers, so that
getting many files from the same server will not do multiple connects /
handshakes. This improves speed. Of course this is only done on files
specified on a single command line and cannot be used between separate curl
invokes.
.SH "PROGRESS METER"
curl normally displays a progress meter during operations, indicating the
amount of transferred data, transfer speeds and estimated time left, etc.

curl displays this data to the terminal by default, so if you invoke curl to
do an operation and it is about to write data to the terminal, it
\fIdisables\fP the progress meter as otherwise it would mess up the output
mixing progress meter and response data.

If you want a progress meter for HTTP POST or PUT requests, you need to
redirect the response output to a file, using shell redirect (>), -o [file] or
similar.

It is not the same case for 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-#\fP is your
friend.
.SH OPTIONS
Options start with one or two dashes. Many of the options require an addition
value next to it.

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, --data for example, requires a space
between it and its value.

Short version options that don't need any additional values can be used
immediately next to each other, like for example you can specify all the
options -O, -L and -v at once as -OLv.

In general, all boolean options are enabled with --\fBoption\fP and yet again
disabled with --\fBno-\fPoption. That is, you use the exact same option name
but prefix it with "no-". However, in this list we mostly only list and show
the --option version of them. (This concept with --no options was added in
7.19.0. Previously most options were toggled on/off on repeated use of the
same command line option.)
.IP "-#, --progress-bar"
Make curl display progress as a simple progress bar instead of the standard,
more informational, meter.
.IP "-0, --http1.0"
(HTTP) Tells curl to use HTTP version 1.0 instead of using its internally
preferred: HTTP 1.1.
.IP "--http1.1"
(HTTP) Tells curl to use HTTP version 1.1. This is the internal default
version. (Added in 7.33.0)
.IP "--http2.0"
(HTTP) Tells curl to issue its requests using HTTP 2.0. This requires that the
underlying libcurl was built to support it. (Added in 7.33.0)
.IP "-1, --tlsv1"
(SSL)
Forces curl to use TLS version 1 when negotiating with a remote TLS server.
.IP "-2, --sslv2"
(SSL)
Forces curl to use SSL version 2 when negotiating with a remote SSL server.
.IP "-3, --sslv3"
(SSL)
Forces curl to use SSL version 3 when negotiating with a remote SSL server.
.IP "-4, --ipv4"
If curl is capable of resolving an address to multiple IP versions (which it
is if it is IPv6-capable), this option tells curl to resolve names to IPv4
addresses only.
.IP "-6, --ipv6"
If curl is capable of resolving an address to multiple IP versions (which it
is if it is IPv6-capable), this option tells curl to resolve names to IPv6
addresses only.
.IP "-a, --append"
(FTP/SFTP) When used in an upload, this will tell curl to append to the target
file instead of overwriting it. If the file doesn't exist, it will be created.
Note that this flag is ignored by some SSH servers (including OpenSSH).
.IP "-A, --user-agent <agent string>"
(HTTP) Specify the User-Agent string to send to the HTTP server. Some badly
done CGIs fail if this field isn't set to "Mozilla/4.0". To encode blanks in
the string, surround the string with single quote marks. This can also be set
with the \fI-H, --header\fP option of course.

If this option is used several times, the last one will be used.
.IP "--anyauth"
(HTTP) Tells curl to figure out authentication method by itself, 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 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.

Note that using --anyauth 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 will fail.
.IP "--bearer"
(IMAP/SMTP) Specify the Bearer Token for OAUTH 2.0 server authentication. The
Bearer Token is used in conjuction with the user name which can be specified
as part of the \fI--url\fP option or the \fI-u, --user\fP option.

The Bearer Token and user name are formatted according to RFC 6750.

If this option is used several times, the last one will be used.
.IP "-b, --cookie <name=data>"
(HTTP)
Pass the data to the HTTP server as a cookie. It is supposedly the
data previously received from the server in a "Set-Cookie:" line.
The data should be in the format "NAME1=VALUE1; NAME2=VALUE2".

If no '=' symbol is used in the line, it is treated as a filename to use to
read previously stored cookie lines from, which should be used in this session
if they match. Using this method also activates the "cookie parser" which will
make curl record incoming cookies too, which may be handy if you're using this
in combination with the \fI-L, --location\fP option. The file format of the
file to read cookies from should be plain HTTP headers or the Netscape/Mozilla
cookie file format.

\fBNOTE\fP that the file specified with \fI-b, --cookie\fP is only used as
input. No cookies will be stored in the file. To store cookies, use the
\fI-c, --cookie-jar\fP option or you could even save the HTTP headers to a file
using \fI-D, --dump-header\fP!

If this option is used several times, the last one will be used.
.IP "-B, --use-ascii"
(FTP/LDAP) Enable ASCII transfer. For FTP, this can also be
enforced by using an URL that ends with ";type=A". This option causes data
sent to stdout to be in text mode for win32 systems.
.IP "--basic"
(HTTP) Tells curl to use HTTP Basic authentication. This 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).
.IP "-c, --cookie-jar <file name>"
(HTTP) Specify to which file you want curl to write all cookies after a
completed operation. Curl writes all cookies previously read from a specified
file as well as all cookies received from remote server(s). If no cookies are
known, no file will be written. The file will be written using the Netscape
cookie file format. If you set the file name to a single dash, "-", the
cookies will be written to stdout.

This command line option will activate the cookie engine that makes curl
record and use cookies. Another way to activate it is to use the \fI-b,
--cookie\fP option.

If the cookie jar can't be created or written to, the whole curl operation
won't fail or even report an error clearly. Using -v will get a warning
displayed, but that is the only visible feedback you get about this possibly
lethal situation.

If this option is used several times, the last specified file name will be
used.
.IP "-C, --continue-at <offset>"
Continue/Resume a previous file transfer at the given offset. The given offset
is the exact number of bytes that will be 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 will not be used by curl.

Use "-C -" to tell curl to automatically find out where/how to resume the
transfer. It then uses the given output/input files to figure that out.

If this option is used several times, the last one will be used.
.IP "--ciphers <list of ciphers>"
(SSL) Specifies which ciphers to use in the connection. The list of ciphers
must specify valid ciphers. Read up on SSL cipher list details on this URL:
\fIhttp://www.openssl.org/docs/apps/ciphers.html\fP

NSS ciphers are done differently than OpenSSL and GnuTLS. The full list of NSS
ciphers is in the NSSCipherSuite entry at this URL:
\fIhttp://git.fedorahosted.org/cgit/mod_nss.git/plain/docs/mod_nss.html#Directives\fP

If this option is used several times, the last one will be used.
.IP "--compressed"
(HTTP) Request a compressed response using one of the algorithms curl
supports, and save the uncompressed document.  If this option is used and the
server sends an unsupported encoding, curl will report an error.
.IP "--connect-timeout <seconds>"
Maximum time in seconds that you allow the connection to the server to take.
This only limits the connection phase, once curl has connected this option is
of no more use.  Since 7.32.0, this option accepts decimal values, but the
actual timeout will decrease in accuracy as the specified timeout increases in
decimal precision. See also the \fI-m, --max-time\fP option.

If this option is used several times, the last one will be used.
.IP "--create-dirs"
When used in conjunction with the \fI-o\fP option, curl will create the
necessary local directory hierarchy as needed. This option creates the dirs
mentioned with the \fI-o\fP option, nothing else. If the \fI-o\fP file name
uses no dir or if the dirs it mentions already exist, no dir will be created.

To create remote directories when using FTP or SFTP, try
\fI--ftp-create-dirs\fP.
.IP "--crlf"
(FTP) Convert LF to CRLF in upload. Useful for MVS (OS/390).
.IP "--crlfile <file>"
(HTTPS/FTPS) Provide a file using PEM format with a Certificate Revocation
List that may specify peer certificates that are to be considered revoked.

If this option is used several times, the last one will be used.

(Added in 7.19.7)
.IP "-d, --data <data>"
(HTTP) Sends 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 will cause curl to pass the data to the server
using the content-type application/x-www-form-urlencoded.  Compare to
\fI-F, --form\fP.

\fI-d, --data\fP is the same as \fI--data-ascii\fP. 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 will be merged together with a separating
&-symbol. Thus, using '-d name=daniel -d skill=lousy' would generate a post
chunk that looks like \&'name=daniel&skill=lousy'.

If you start the data with the letter @, the rest should be a file name to
read the data from, or - if you want curl to read the data from stdin.  The
contents of the file must already be URL-encoded. Multiple files can also be
specified. Posting data from a file named 'foobar' would thus be done with
\fI--data\fP @filename. When --data is told to read from a file like that,
carriage returns and newlines will be stripped out.
.IP "-D, --dump-header <file>"
Write the protocol headers to the specified file.

This option is handy to use when you want to store the headers that an HTTP
site sends to you. Cookies from the headers could then be read in a second
curl invocation by using the \fI-b, --cookie\fP option! The
\fI-c, --cookie-jar\fP option is however a better way to store cookies.

When used in FTP, the FTP server response lines are considered being "headers"
and thus are saved there.

If this option is used several times, the last one will be used.

.IP "--data-ascii <data>"
See \fI-d, --data\fP.
.IP "--data-binary <data>"
(HTTP) This posts data exactly as specified with no extra processing
whatsoever.

If you start the data with the letter @, the rest should be a filename.  Data
is posted in a similar manner as \fI--data-ascii\fP does, except that newlines
and carriage returns are preserved and conversions are never done.

If this option is used several times, the ones following the first will append
data as described in \fI-d, --data\fP.
.IP "--data-urlencode <data>"
(HTTP) This posts data, similar to the other --data options with the exception
that this performs URL-encoding. (Added in 7.18.0)

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"
This will make curl URL-encode the content and pass that on. Just be careful
so that the content doesn't contain any = or @ symbols, as that will then make
the syntax match one of the other cases below!
.IP "=content"
This will make curl URL-encode the content and pass that on. The preceding =
symbol is not included in the data.
.IP "name=content"
This will make curl URL-encode the content part and pass that on. Note that
the name part is expected to be URL-encoded already.
.IP "@filename"
This will make curl load data from the given file (including any newlines),
URL-encode that data and pass it on in the POST.
.IP "name@filename"
This will make curl 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 "--delegation LEVEL"
Set \fILEVEL\fP to tell the server what it is allowed to delegate when it
comes to user credentials. Used with GSS/kerberos.
.RS
.IP "none"
Don't 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 "--digest"
(HTTP) Enables HTTP Digest authentication. This is an authentication scheme
that prevents the password from being sent over the wire in clear text. Use
this in combination with the normal \fI-u, --user\fP option to set user name
and password. See also \fI--ntlm\fP, \fI--negotiate\fP and \fI--anyauth\fP for
related options.

If this option is used several times, only the first one is used.
.IP "--disable-eprt"
(FTP) Tell curl to disable the use of the EPRT and LPRT commands when doing
active FTP transfers. Curl will normally always first attempt to use EPRT,
then LPRT before using PORT, but with this option, it will use PORT right
away. EPRT and LPRT are extensions to the original FTP protocol, and may not
work on all servers, but they enable more functionality in a better way than
the traditional PORT command.

\fB--eprt\fP can be used to explicitly enable EPRT again and \fB--no-eprt\fP
is an alias for \fB--disable-eprt\fP.

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.
.IP "--disable-epsv"
(FTP) Tell curl to disable the use of the EPSV command when doing passive FTP
transfers. Curl will normally always first attempt to use EPSV before PASV,
but with this option, it will not try using EPSV.

\fB--epsv\fP can be used to explicitly enable EPSV again and \fB--no-epsv\fP
is an alias for \fB--disable-epsv\fP.

Disabling EPSV only changes the passive behavior. If you want to switch to
active mode you need to use \fI-P, --ftp-port\fP.
.IP "-e, --referer <URL>"
(HTTP) Sends the "Referer Page" information to the HTTP server. 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 --referer 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 don't set an initial --referer.

If this option is used several times, the last one will be used.
.IP "-E, --cert <certificate[:password]>"
(SSL) Tells curl to 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 isn't specified, it will be queried
for on the terminal. Note that this option assumes a \&"certificate" file that
is the private key and the private certificate concatenated! See \fI--cert\fP
and \fI--key\fP to specify them independently.

If curl is built against the NSS SSL library then this option can tell
curl the nickname of the certificate to use within the NSS database defined
by the environment variable SSL_DIR (or by default /etc/pki/nssdb). If the
NSS PEM PKCS#11 module (libnsspem.so) is available then PEM files may be
loaded. If you want to use a file from the current directory, please precede
it with "./" prefix, in order to avoid confusion with a nickname.  If the
nickname contains ":", it needs to be preceded by "\\" so that it is not
recognized as password delimiter.  If the nickname contains "\\", it needs to
be escaped as "\\\\" so that it is not recognized as an escape character.

(iOS and Mac OS X 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.

If this option is used several times, the last one will be used.
.IP "--engine <name>"
Select the OpenSSL crypto engine to use for cipher
operations. Use \fI--engine list\fP to print a list of build-time supported
engines. Note that not all (or none) of the engines may be available at
run-time.
.IP "--environment"
(RISC OS ONLY) Sets a range of environment variables, using the names the
\fI-w\fP option supports, to allow easier extraction of useful information
after having run curl.
.IP "--egd-file <file>"
(SSL) Specify the path name to the Entropy Gathering Daemon socket. The socket
is used to seed the random engine for SSL connections. See also the
\fI--random-file\fP option.
.IP "--cert-type <type>"
(SSL) Tells curl what certificate type the provided certificate is in. PEM,
DER and ENG are recognized types.  If not specified, PEM is assumed.

If this option is used several times, the last one will be used.
.IP "--cacert <CA certificate>"
(SSL) Tells curl to 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 'CURL_CA_BUNDLE' if it is
set, and uses the given path as a path to a CA cert bundle. This option
overrides that variable.

The windows version of curl will automatically look for a CA certs file named
\'curl-ca-bundle.crt\', either in the same directory as curl.exe, or in the
Current Working Directory, or in any folder along your PATH.

If curl is built against the NSS SSL library, the NSS PEM PKCS#11 module
(libnsspem.so) needs to be available for this option to work properly.

If this option is used several times, the last one will be used.
.IP "--capath <CA certificate directory>"
(SSL) Tells curl to use the specified certificate directory to verify the
peer. Multiple paths can be provided by separating them with ":" (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 will be ignored, and if it is
used several times, the last one will be used.
.IP "-f, --fail"
(HTTP) Fail silently (no output at all) on server errors. This is mostly done
to better enable scripts etc to better deal with failed attempts. 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 flag
will prevent curl from outputting that and return error 22.

This method is not fail-safe and there are occasions where non-successful
response codes will slip through, especially when authentication is involved
(response codes 401 and 407).
.IP "-F, --form <name=content>"
(HTTP) This lets curl emulate a filled-in form in which a user has pressed the
submit button. This causes curl to POST data using the Content-Type
multipart/form-data according to RFC 2388. This enables uploading of binary
files etc. To force the 'content' part to be a file, prefix the file name
with an @ sign. To just get the content part from a file, prefix the file name
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 get the contents for that text field from a file.

Example, to send your password file to the server, where
\&'password' is the name of the form-field to which /etc/passwd will be the
input:

\fBcurl\fP -F password=@/etc/passwd www.mypasswords.com

To read content from stdin instead of a file, use - as the filename. This goes
for both @ and < constructs.

You can also tell curl what Content-Type to use by using 'type=', in a manner
similar to:

\fBcurl\fP -F "web=@index.html;type=text/html" url.com

or

\fBcurl\fP -F "name=daniel;type=text/foo" url.com

You can also explicitly change the name field of a file upload part by setting
filename=, like this:

\fBcurl\fP -F "file=@localfile;filename=nameinpost" url.com

If filename/path contains ',' or ';', it must be quoted by double-quotes like:

\fBcurl\fP -F "file=@\\"localfile\\";filename=\\"nameinpost\\"" url.com

or

\fBcurl\fP -F 'file=@"localfile";filename="nameinpost"' url.com

Note that if a filename/path is quoted by double-quotes, any double-quote
or backslash within the filename must be escaped by backslash.

See further examples and details in the MANUAL.

This option can be used multiple times.
.IP "--ftp-account [data]"
(FTP) When an FTP server asks for "account data" after user name and password
has been provided, this data is sent off using the ACCT command. (Added in
7.13.0)

If this option is used several times, the last one will be used.
.IP "--ftp-alternative-to-user <command>"
(FTP) If authenticating with the USER and PASS commands fails, send this
command.  When connecting to Tumbleweed's Secure Transport server over FTPS
using a client certificate, using "SITE AUTH" will tell the server to retrieve
the username from the certificate. (Added in 7.15.5)
.IP "--ftp-create-dirs"
(FTP/SFTP) When an FTP or SFTP URL/operation uses a path that doesn't
currently exist on the server, the standard behavior of curl is to
fail. Using this option, curl will instead attempt to create missing
directories.
.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
curl does a single CWD operation for each path part in the given URL. For deep
hierarchies this means very many commands. This is how RFC 1738 says it should
be done. This is the default but the slowest behavior.
.IP nocwd
curl does no CWD at all. curl will do SIZE, RETR, STOR etc and give a full
path to the server for all these commands. This is the fastest behavior.
.IP singlecwd
curl does one CWD with the full target directory and then operates 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
(Added in 7.15.1)
.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. (Added in 7.11.0)

If this option is used several times, only the first one is used. Undoing an
enforced passive really isn't doable but you must then instead enforce the
correct \fI-P, --ftp-port\fP again.

Passive mode means that curl will try the EPSV command first and then PASV,
unless \fI--disable-epsv\fP is used.
.IP "--ftp-skip-pasv-ip"
(FTP) Tell curl to not use the IP address the server suggests in its response
to curl's PASV command when curl connects the data connection. Instead curl
will re-use the same IP address it already uses for the control
connection. (Added in 7.14.2)

This option has no effect if PORT, EPRT or EPSV is used instead of PASV.
.IP "--ftp-pret"
(FTP) Tell curl to 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.
(Added in 7.20.x)
.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 will be unencrypted. This allows
NAT routers to follow the FTP transaction. The default mode is
passive. See \fI--ftp-ssl-ccc-mode\fP for other modes.
(Added in 7.16.1)
.IP "--ftp-ssl-ccc-mode [active/passive]"
(FTP) Use CCC (Clear Command Channel)
Sets the CCC mode. The passive mode will not initiate the shutdown, but
instead wait for the server to do it, and will not reply to the
shutdown from the server. The active mode initiates the shutdown and
waits for a reply from the server.
(Added in 7.16.2)
.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 doesn't support SSL/TLS.  (Added in 7.16.0)
that can still be used but will be removed in a future version.
.IP "--form-string <name=string>"
(HTTP) Similar to \fI--form\fP except that the value string for the named
parameter is used literally. Leading \&'@' and \&'<' characters, and the
\&';type=' string in the value have no special meaning. Use this in preference
to \fI--form\fP if there's any possibility that the string value may
accidentally trigger the \&'@' or \&'<' features of \fI--form\fP.
.IP "-g, --globoff"
This option switches off the "URL globbing parser". When you set this option,
you can specify URLs that contain the letters {}[] without having them being
interpreted by curl itself. Note that these letters are not normal legal URL
contents but they should be encoded according to the URI standard.
.IP "-G, --get"
When used, this option will make all data specified with \fI-d, --data\fP or
\fI--data-binary\fP to be used in an HTTP GET request instead of the POST
request that otherwise would be used. The data will be appended to the URL
with a '?' separator.

If used in combination with -I, the POST data will instead be appended to the
URL with a HEAD request.

If this option is used several times, only the first one is used. This is
because undoing a GET doesn't make sense, but you should then instead enforce
the alternative method you prefer.
.IP "-H, --header <header>"
(HTTP) Extra header to use when getting a web page. 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 will be 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're 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 will make 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 will only mess things up
for you.

See also the \fI-A, --user-agent\fP and \fI-e, --referer\fP options.

This option can be used multiple times to add/replace/remove multiple headers.
.IP "--hostpubmd5 <md5>"
(SCP/SFTP) Pass a string containing 32 hexadecimal digits. The string should
be the 128 bit MD5 checksum of the remote host's public key, curl will refuse
the connection with the host unless the md5sums match. (Added in 7.17.1)
.IP "--ignore-content-length"
(HTTP)
Ignore the Content-Length header. This is particularly useful for servers
running Apache 1.x, which will report incorrect Content-Length for files
larger than 2 gigabytes.
.IP "-i, --include"
(HTTP) Include the HTTP-header in the output. The HTTP-header includes things
like server-name, date of the document, HTTP-version and more...
.IP "-I, --head"
(HTTP/FTP/FILE)
Fetch the HTTP-header 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 file, curl displays the file size and last modification
time only.
.IP "--interface <name>"
Perform an operation using a specified interface. You can enter interface
name, IP address or host name. An example could look like:

 curl --interface eth0:1 http://www.netscape.com/

If this option is used several times, the last one will be used.
.IP "-j, --junk-session-cookies"
(HTTP) When curl is told to read cookies from a given file, this option will
make it discard all "session cookies". This will basically have the same effect
as if a new session is started. Typical browsers always discard session
cookies when they're closed down.
.IP "-J, --remote-header-name"
(HTTP) This option tells the \fI-O, --remote-name\fP option to use the
server-specified Content-Disposition filename instead of extracting a filename
from the URL.
.IP "-k, --insecure"
(SSL) This option explicitly allows curl to perform "insecure" SSL connections
and transfers. All SSL connections are attempted to be made secure by using
the CA certificate bundle installed by default. This makes all connections
considered "insecure" fail unless \fI-k, --insecure\fP is used.

See this online resource for further details:
\fBhttp://curl.haxx.se/docs/sslcerts.html\fP
.IP "-K, --config <config file>"
Specify which config file to read curl arguments from. The config file is a
text file in which command line arguments can be written which then will be
used as if they were written on the actual command line. Options and their
parameters must be specified on the same config file line, separated by
whitespace, colon, the equals sign or any combination thereof (however,
the preferred separator is the equals sign). If the parameter is to contain
whitespace, the parameter must be enclosed within quotes. 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 column of a config line is a '#' character, the rest of the line will be
treated as a comment. Only write one option per physical line in the config
file.

Specify the filename to -K, --config as '-' 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:

url = "http://curl.haxx.se/docs/"

Long option names can optionally be given in the config file without the
initial double dashes.

When curl is invoked, it always (unless \fI-q\fP is used) checks for a default
config file and uses it if found. The default config file is checked for in
the following places in this order:

1) curl tries to find the "home dir": It first checks for the CURL_HOME and
then the HOME environment variables. Failing that, it uses getpwuid() on
UNIX-like systems (which returns the home dir given the current user in your
system). On Windows, it then checks for the APPDATA variable, or as a last
resort the '%USERPROFILE%\\Application Data'.

2) On windows, if there is no _curlrc file in the home dir, it checks for one
in the same dir the curl executable is placed. On UNIX-like systems, it will
simply try to load .curlrc from the determined home dir.

.nf
# --- Example file ---
# this is a comment
url = "curl.haxx.se"
output = "curlhere.html"
user-agent = "superagent/1.0"

# and fetch another URL too
url = "curl.haxx.se/docs/manpage.html"
-O
referer = "http://nowhereatall.com/"
# --- End of example file ---
.fi

This option can be used multiple times to load multiple config files.
.IP "--keepalive-time <seconds>"
This option sets 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, recent AIX, HP-UX and more). This
option has no effect if \fI--no-keepalive\fP is used. (Added in 7.18.0)

If this option is used several times, the last one will be used. If
unspecified, the option defaults to 60 seconds.
.IP "--key <key>"
(SSL/SSH) Private key file name. Allows you to provide your private key in this
separate file.

If this option is used several times, the last one will be used.
.IP "--key-type <type>"
(SSL) 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 this option is used several times, the last one will be used.
.IP "--krb <level>"
(FTP) Enable Kerberos authentication and use. The level must be entered and
should be one of 'clear', 'safe', 'confidential', or 'private'. Should you use
a level that is not one of these, 'private' will instead be used.

This option requires a library built with kerberos4 or GSSAPI
(GSS-Negotiate) support. This is not very common. Use \fI-V, --version\fP to
see if your curl supports it.

If this option is used several times, the last one will be used.
.IP "-l, --list-only"
(FTP)
When listing an FTP directory, this switch forces a name-only view.
Especially useful if you want to machine-parse the contents of an FTP
directory since the normal directory view doesn't use a standard look
or format.

This option causes an FTP NLST command to be sent.  Some FTP servers
list only files in their response to NLST; they do not include
subdirectories and symbolic links.

.IP "-L, --location"
(HTTP/HTTPS) 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 will make curl redo the request on the new place. If used together
with \fI-i, --include\fP or \fI-I, --head\fP, headers from all requested pages
will be shown. When authentication is used, curl only sends its credentials to
the initial host. If a redirect takes curl to a different host, it won't be
able to intercept the user+password. See also \fI--location-trusted\fP on how
to change this. You can limit the amount of redirects to follow by using the
\fI--max-redirs\fP option.

When curl follows a redirect and the request is not a plain GET (for example
POST or PUT), it will do 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 will
re-send the following request using the same unmodified method.
.IP "--libcurl <file>"
Append this option to any ordinary curl command line, and you will get a
libcurl-using C source code written to the file that does the equivalent
of what your command-line operation does!

If this option is used several times, the last given file name will be
used. (Added in 7.16.1)
.IP "--limit-rate <speed>"
Specify the maximum transfer rate you want curl to use. This feature is useful
if you have a limited pipe and you'd like your transfer not to use your entire
bandwidth.

The given speed is measured in bytes/second, unless a suffix is appended.
Appending 'k' or 'K' will count the number as kilobytes, 'm' or M' makes it
megabytes, while 'g' or 'G' makes it gigabytes. Examples: 200K, 3m and 1G.

The given rate is the average speed counted during the entire transfer. It
means that curl might use higher transfer speeds in short bursts, but over
time it uses no more than the given rate.

If you also use the \fI-Y, --speed-limit\fP option, that option will take
precedence and might cripple the rate-limiting slightly, to help keeping the
speed-limit logic working.

If this option is used several times, the last one will be used.
.IP "--local-port <num>[-num]"
Set a preferred number or range of local port numbers to use for the
connection(s).  Note that port numbers by nature are a scarce resource that
will be busy at times so setting this range to something too narrow might
cause unnecessary connection setup failures. (Added in 7.15.2)
.IP "--location-trusted"
(HTTP/HTTPS) Like \fI-L, --location\fP, but will allow sending the name +
password to all hosts that the site may redirect to. This may or may not
introduce a security breach if the site redirects you to a site to which
you'll send your authentication info (which is plaintext in the case of HTTP
Basic authentication).
.IP "-m, --max-time <seconds>"
Maximum time in seconds that you allow the whole operation to take.  This is
useful for preventing your batch jobs from hanging for hours due to slow
networks or links going down.  Since 7.32.0, this option accepts decimal
values, but the actual timeout will decrease in accuracy as the specified
timeout increases in decimal precision.  See also the \fI--connect-timeout\fP
option.

If this option is used several times, the last one will be used.
.IP "--mail-auth <address>"
(SMTP) Specify a single address. This will be used to specify the
authentication address (identity) of a submitted message that is being relayed
to another server.

(Added in 7.25.0)
.IP "--mail-from <address>"
(SMTP) Specify a single address that the given mail should get sent from.

(Added in 7.20.0)
.IP "--max-filesize <bytes>"
Specify the maximum size (in bytes) of a file to download. If the file
requested is larger than this value, the transfer will not start and curl will
return with exit code 63.

\fBNOTE:\fP The file size is not always known prior to download, and for such
files this option has no effect even if the file transfer ends up being larger
than this given limit. This concerns both FTP and HTTP transfers.
.IP "--mail-rcpt <address>"
(SMTP) Specify a single address that the given mail should get sent to. This
option can be used multiple times to specify many recipients.

(Added in 7.20.0)
.IP "--max-redirs <num>"
Set maximum number of redirection-followings allowed. If \fI-L, --location\fP
is used, this option can be used to prevent curl from following redirections
\&"in absurdum". By default, the limit is set to 50 redirections. Set this
option to -1 to make it limitless.

If this option is used several times, the last one will be used.
.IP "--metalink"
This option can tell curl to parse and process a given URI as Metalink file
(both version 3 and 4 (RFC 5854) are supported) and make use of the mirrors
listed within for failover if there are errors (such as the file or server not
being available). It will also verify the hash of the file after the download
completes. The Metalink file itself is downloaded and processed in memory and
not stored in the local file system.

Example to use a remote Metalink file:

\fBcurl\fP --metalink http://www.example.com/example.metalink

To use a Metalink file in the local file system, use FILE protocol
(file://):

\fBcurl\fP --metalink file://example.metalink

Please note that if FILE protocol is disabled, there is no way to use
a local Metalink file at the time of this writing. Also note that if
\fI--metalink\fP and \fI--include\fP are used together, \fI--include\fP will be
ignored. This is because including headers in the response will break
Metalink parser and if the headers are included in the file described
in Metalink file, hash check will fail.

(Added in 7.27.0, if built against the libmetalink library.)
.IP "-n, --netrc"
Makes curl scan the \fI.netrc\fP (\fI_netrc\fP on Windows) file in the user's
home directory for login name and password. This is typically used for FTP on
UNIX. If used with HTTP, curl will enable user authentication. See
.BR netrc(4)
or
.BR ftp(1)
for details on the file format. Curl will not complain if that file
doesn't have the right permissions (it should not be either world- or
group-readable). The environment variable "HOME" is used to find the home
directory.

A quick and very simple example of how to setup a \fI.netrc\fP to allow curl
to FTP to the machine host.domain.com with user name \&'myself' and password
\&'secret' should look similar to:

.B "machine host.domain.com login myself password secret"
.IP "-N, --no-buffer"
Disables the buffering of the output stream. In normal work situations, curl
will use a standard buffered output stream that will have the effect that it
will output the data in chunks, not necessarily exactly when the data arrives.
Using this option will disable that buffering.

Note that this is the negated option name documented. You can thus use
\fI--buffer\fP to enforce the buffering.
.IP "--netrc-file"
This option is similar to \fI--netrc\fP, except that you provide the path
(absolute or relative) to the netrc file that Curl should use.
You can only specify one netrc file per invocation. If several
\fI--netrc-file\fP options are provided, only the \fBlast one\fP will be used.
(Added in 7.21.5)

This option overrides any use of \fI--netrc\fP as they are mutually exclusive.
It will also abide by \fI--netrc-optional\fP if specified.

.IP "--netrc-optional"
Very similar to \fI--netrc\fP, but this option makes the .netrc usage
\fBoptional\fP and not mandatory as the \fI--netrc\fP option does.

.IP "--negotiate"
(HTTP) Enables GSS-Negotiate authentication. The GSS-Negotiate method was
designed by Microsoft and is used in their web applications. It is primarily
meant as a support for Kerberos5 authentication but may be also used along
with another authentication method. For more information see IETF draft
draft-brezak-spnego-http-04.txt.

If you want to enable Negotiate for your proxy authentication, then use
\fI--proxy-negotiate\fP.

This option requires a library built with GSSAPI support. This is
not very common. Use \fI-V, --version\fP to see if your version supports
GSS-Negotiate.

When using this option, you must also provide a fake \fI-u, --user\fP option to
activate the authentication code properly. Sending a '-u :' is enough as the
user name and password from the \fI-u\fP option aren't actually used.

If this option is used several times, only the first one is used.
.IP "--no-keepalive"
Disables the use of keepalive messages on the TCP connection, as by default
curl enables them.

Note that this is the negated option name documented. You can thus use
\fI--keepalive\fP to enforce keepalive.
.IP "--no-sessionid"
(SSL) Disable curl's 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. (Added in 7.16.0)

Note that this is the negated option name documented. You can thus use
\fI--sessionid\fP to enforce session-ID caching.
.IP "--noproxy <no-proxy-list>"
Comma-separated list of hosts which do not 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.  (Added in 7.19.4).
.IP "--ntlm"
(HTTP) Enables 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.

This option requires a library built with SSL support. Use
\fI-V, --version\fP to see if your curl supports NTLM.

If this option is used several times, only the first one is used.
.IP "-o, --output <file>"
Write output to <file> instead of stdout. If you are using {} or [] to fetch
multiple documents, you can use '#' followed by a number in the <file>
specifier. That variable will be replaced with the current string for the URL
being fetched. Like in:

  curl http://{one,two}.site.com -o "file_#1.txt"

or use several variables like:

  curl http://{site,host}.host[1-5].com -o "#1_#2"

You may use this option as many times as the number of URLs you have.

See also the \fI--create-dirs\fP option to create the local directories
dynamically. Specifying the output as '-' (a single dash) will force the
output to be done to stdout.
.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 remote file name to use for saving is extracted from the given URL,
nothing else.

Consequentially, the file will be saved in the current working directory. If
you want the file saved in a different directory, make sure you change current
working directory before you invoke curl with the \fB-O, --remote-name\fP flag!

You may use this option as many times as the number of URLs you have.
.IP "-p, --proxytunnel"
When an HTTP proxy is used (\fI-x, --proxy\fP), this option will cause non-HTTP
protocols to attempt to tunnel through the proxy instead of merely using it to
do HTTP-like operations. The tunnel approach is made with the HTTP proxy
CONNECT request and requires that the proxy allows direct connect to the
remote port number curl wants to tunnel through to.
.IP "-P, --ftp-port <address>"
(FTP) Reverses the default initiator/listener roles when connecting with
FTP. This switch makes curl use active mode. In practice, curl then tells the
server to connect back to the client's 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
i.e "eth0" to specify which interface's IP address you want to use (Unix only)
.IP "IP address"
i.e "192.168.10.1" to specify the exact IP address
.IP "host name"
i.e "my.host.domain" to specify the machine
.IP "-"
make curl pick the same IP address that is already used for the control
connection
.RE

If this option is used several times, the last one will be used. 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++.

Starting in 7.19.5, you can 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.
.IP "--pass <phrase>"
(SSL/SSH) Passphrase for the private key

If this option is used several times, the last one will be used.
.IP "--post301"
(HTTP) Tells curl to respect RFC 2616/10.3.2 and not convert POST requests
into GET requests when following a 301 redirection. The non-RFC behaviour 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
(Added in 7.17.1)
.IP "--post302"
(HTTP) Tells curl to respect RFC 2616/10.3.2 and not convert POST requests
into GET requests when following a 302 redirection. The non-RFC behaviour 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
(Added in 7.19.1)
.IP "--post303"
(HTTP) Tells curl to respect RFC 2616/10.3.2 and not convert POST requests
into GET requests when following a 303 redirection. The non-RFC behaviour 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
(Added in 7.26.0)
.IP "--proto <protocols>"
Tells curl to use the listed protocols for its initial retrieval. Protocols
are evaluated left to right, are comma separated, and are each a protocol
name or 'all', optionally prefixed by zero or more modifiers. Available
modifiers are:
.RS
.TP 3
.B +
Permit this protocol in addition to protocols already permitted (this is
the default if no modifier is used).
.TP
.B -
Deny this protocol, removing it from the list of protocols already permitted.
.TP
.B =
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:
.RS
.TP 15
.B --proto -ftps
uses the default protocols, but disables ftps
.TP
.B  --proto -all,https,+http
only enables http and https
.TP
.B --proto =http,https
also only enables http and https
.RE
.IP
Unknown 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.

(Added in 7.20.2)
.IP "--proto-redir <protocols>"
Tells curl to use the listed protocols after a redirect. See --proto for
how protocols are represented.

(Added in 7.20.2)
.IP "--proxy-anyauth"
Tells curl to pick a suitable authentication method when communicating with
the given proxy. This might cause an extra request/response round-trip. (Added
in 7.13.2)
.IP "--proxy-basic"
Tells curl to 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.
.IP "--proxy-digest"
Tells curl to use HTTP Digest authentication when communicating with the given
proxy. Use \fI--digest\fP for enabling HTTP Digest with a remote host.
.IP "--proxy-negotiate"
Tells curl to use HTTP Negotiate authentication when communicating
with the given proxy. Use \fI--negotiate\fP for enabling HTTP Negotiate
with a remote host. (Added in 7.17.1)
.IP "--proxy-ntlm"
Tells curl to use HTTP NTLM authentication when communicating with the given
proxy. Use \fI--ntlm\fP for enabling NTLM with a remote host.
.IP "--proxy1.0 <proxyhost[: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 will specify an HTTP 1.0
protocol instead of the default HTTP 1.1.
.IP "--pubkey <key>"
(SSH) Public key file name. Allows you to provide your public key in this
separate file.

If this option is used several times, the last one will be used.
.IP "-q"
If used as the first parameter on the command line, the \fIcurlrc\fP config
file will not be read and used. See the \fI-K, --config\fP for details on the
default config file search path.
.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 PWD
command in an FTP transfer, to be exact). To make commands take place after a
successful transfer, prefix them with a dash '-'.  To make commands be sent
after curl has changed the working directory, just before the transfer
command(s), prefix the command with a '+' (this is only supported for
FTP). You may specify any number of commands. If the server returns failure
for one of the commands, the entire operation will be 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.  This option can be used
multiple times. When speaking to an FTP server, prefix the command with an
asterisk (*) to make curl continue even if the command fails as by default
curl will stop at first failure.

SFTP is a binary protocol. Unlike for FTP, curl interprets SFTP quote commands
itself before sending them to the server.  File names may be quoted
shell-style to embed spaces or special characters.  Following is the list of
all supported SFTP quote commands:
.RS
.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 "pwd"
The pwd command returns the absolute pathname 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 "-r, --range <range>"
(HTTP/FTP/SFTP/FILE) Retrieve a byte range (i.e a partial document) from a
HTTP/1.1, FTP or SFTP server or a local FILE. Ranges can be specified
in a number of ways.
.RS
.TP 10
.B 0-499
specifies the first 500 bytes
.TP
.B 500-999
specifies the second 500 bytes
.TP
.B -500
specifies the last 500 bytes
.TP
.B 9500-
specifies the bytes from offset 9500 and forward
.TP
.B 0-0,-1
specifies the first and last byte only(*)(H)
.TP
.B 500-700,600-799
specifies 300 bytes from offset 500(H)
.TP
.B 100-199,500-599
specifies two separate 100-byte ranges(*)(H)
.RE

(*) = NOTE that this will cause the server to reply with a multipart
response!

Only digit characters (0-9) are valid in the 'start' and 'stop' fields of the
\&'start-stop' range syntax. If a non-digit character is given in the range,
the server's response will be unspecified, depending on the server's
configuration.

You should also be aware that many HTTP/1.1 servers do not have this feature
enabled, so that when you attempt to get a range, you'll instead get the whole
document.

FTP and SFTP range downloads only support the simple 'start-stop' syntax
(optionally with one of the numbers omitted). FTP use depends on the extended
FTP command SIZE.

If this option is used several times, the last one will be used.
.IP "-R, --remote-time"
When used, this will make curl attempt to figure out the timestamp of the
remote file, and if that is available make the local file get that same
timestamp.
.IP "--random-file <file>"
(SSL) Specify the path name to file containing what will be considered as
random data. The data is used to seed the random engine for SSL connections.
See also the \fI--egd-file\fP option.
.IP "--raw"
(HTTP) When used, it disables all internal HTTP decoding of content or transfer
encodings and instead makes them passed on unaltered, raw. (Added in 7.16.2)
.IP "--remote-name-all"
This option changes the default action for all given URLs to be dealt with as
if \fI-O, --remote-name\fP were used for each one. So 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. (Added in 7.19.0)
.IP "--resolve <host:port:address>"
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 will be used for. It means
you need several entries if you want to provide address for the same host but
different ports.

This option can be used many times to add many host names to resolve.

(Added in 7.21.3)
.IP "--retry <num>"
If a transient error is returned when curl tries to perform a transfer, it
will retry 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 5xx response code.

When curl is about to retry a transfer, it will first wait one second and then
for all forthcoming retries it will double the waiting time until it reaches
10 minutes which then will be the delay 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. (Added in 7.12.3)

If this option is used several times, the last one will be used.
.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 will make curl use the default backoff time.
(Added in 7.12.3)

If this option is used several times, the last one will be used.
.IP "--retry-max-time <seconds>"
The retry timer is reset before the first transfer attempt. Retries will be
done as usual (see \fI--retry\fP) as long as the timer hasn't reached this
given limit. Notice that if the timer hasn't reached the limit, the request
will be made and while performing, it may take longer than this given time
period. To limit a single request\'s maximum time, use \fI-m, --max-time\fP.
Set this option to zero to not timeout retries. (Added in 7.12.3)

If this option is used several times, the last one will be used.
.IP "-s, --silent"
Silent or quiet mode. Don't show progress meter or error messages.  Makes Curl
mute. It will still output the data you ask for, potentially even to the
terminal/stdout unless you redirect it.
.IP "--sasl-ir"
Enable initial response in SASL authentication.
(Added in 7.31.0)
.IP "-S, --show-error"
When used with \fI-s\fP it makes curl show an error message if it fails.
.IP "--ssl"
(FTP, POP3, IMAP, SMTP) Try to use SSL/TLS for the connection.  Reverts to a
non-secure connection if the server doesn't support SSL/TLS.  See also
\fI--ftp-ssl-control\fP and \fI--ssl-reqd\fP for different levels of
encryption required. (Added in 7.20.0)

This option was formerly known as \fI--ftp-ssl\fP (Added in 7.11.0). That
option name can still be used but will be removed in a future version.
.IP "--ssl-reqd"
(FTP, POP3, IMAP, SMTP) Require SSL/TLS for the connection.  Terminates the
connection if the server doesn't support SSL/TLS. (Added in 7.20.0)

This option was formerly known as \fI--ftp-ssl-reqd\fP (added in 7.15.5). That
option name can still be used but will be removed in a future version.
.IP "--ssl-allow-beast"
(SSL) This option tells curl to not work around a security flaw in the SSL3
and TLS1.0 protocols known as BEAST.  If this option isn't used, the SSL layer
may use work-arounds known to cause interoperability problems with some older
SSL implementations. WARNING: this option loosens the SSL security, and by
using this flag you ask for exactly that.  (Added in 7.25.0)
.IP "--socks4 <host[:port]>"
Use the specified SOCKS4 proxy. If the port number is not specified, it is
assumed at port 1080. (Added in 7.15.2)

This option overrides any previous use of \fI-x, --proxy\fP, as they are
mutually exclusive.

Since 7.21.7, this option is superfluous since you can specify a socks4 proxy
with \fI-x, --proxy\fP using a socks4:// protocol prefix.

If this option is used several times, the last one will be used.
.IP "--socks4a <host[:port]>"
Use the specified SOCKS4a proxy. If the port number is not specified, it is
assumed at port 1080. (Added in 7.18.0)

This option overrides any previous use of \fI-x, --proxy\fP, as they are
mutually exclusive.

Since 7.21.7, this option is superfluous since you can specify a socks4a proxy
with \fI-x, --proxy\fP using a socks4a:// protocol prefix.

If this option is used several times, the last one will be used.
.IP "--socks5-hostname <host[:port]>"
Use the specified SOCKS5 proxy (and let the proxy resolve the host name). If
the port number is not specified, it is assumed at port 1080. (Added in
7.18.0)

This option overrides any previous use of \fI-x, --proxy\fP, as they are
mutually exclusive.

Since 7.21.7, this option is superfluous since you can specify a socks5
hostname proxy with \fI-x, --proxy\fP using a socks5h:// protocol prefix.

If this option is used several times, the last one will be used. (This option
was previously wrongly documented and used as --socks without the number
appended.)
.IP "--socks5 <host[:port]>"
Use the specified SOCKS5 proxy - but resolve the host name locally. If the
port number is not specified, it is assumed at port 1080.

This option overrides any previous use of \fI-x, --proxy\fP, as they are
mutually exclusive.

Since 7.21.7, this option is superfluous since you can specify a socks5 proxy
with \fI-x, --proxy\fP using a socks5:// protocol prefix.

If this option is used several times, the last one will be used. (This option
was previously wrongly documented and used as --socks without the number
appended.)

This option (as well as \fI--socks4\fP) does not work with IPV6, FTPS or LDAP.
.IP "--socks5-gssapi-service <servicename>"
The default service name for a socks server is rcmd/server-fqdn. This option
allows you to change it.

Examples: --socks5 proxy-name \fI--socks5-gssapi-service\fP sockd would use
sockd/proxy-name --socks5 proxy-name \fI--socks5-gssapi-service\fP
sockd/real-name would use sockd/real-name for cases where the proxy-name does
not match the principal name.  (Added in 7.19.4).
.IP "--socks5-gssapi-nec"
As part of the gssapi 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. (Added in 7.19.4).
.IP "--stderr <file>"
Redirect all writes to stderr to the specified file instead. If the file name
is a plain '-', it is instead written to stdout.

If this option is used several times, the last one will be used.
.IP "-t, --telnet-option <OPT=val>"
Pass options to the telnet protocol. Supported options are:

TTYPE=<term> Sets the terminal type.

XDISPLOC=<X display> Sets the X display location.

NEW_ENV=<var,val> Sets an environment variable.
.IP "-T, --upload-file <file>"
This transfers the specified local file to the remote URL. If there is no file
part in the specified URL, Curl will append the local file name. NOTE that you
must use a trailing / on the last directory to really prove to Curl that there
is no file name or curl will think that your last directory name is the remote
file name to use. That will most likely cause the upload operation to fail. If
this is used on an HTTP(S) server, the PUT command will be used.

Use the file name "-" (a single dash) to use stdin instead of a given file.
Alternately, the file name "." (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.

You can specify one -T for each URL on the command line. Each -T + URL pair
specifies what to upload and to where. curl also supports "globbing" of the -T
argument, meaning that you can upload multiple files to a single URL by using
the same URL globbing style supported in the URL, like this:

curl -T "{file1,file2}" http://www.uploadtothissite.com

or even

curl -T "img[1-1000].png" ftp://ftp.picturemania.com/upload/
.IP "--tcp-nodelay"
Turn on the TCP_NODELAY option. See the \fIcurl_easy_setopt(3)\fP man page for
details about this option. (Added in 7.11.2)
.IP "--tftp-blksize <value>"
(TFTP) Set TFTP BLKSIZE option (must be >512). This is the block size that
curl will try to use when transferring data to or from a TFTP server. By
default 512 bytes will be used.

If this option is used several times, the last one will be used.

(Added in 7.20.0)
.IP "--tlsauthtype <authtype>"
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".
(Added in 7.21.4)
.IP "--tlsuser <user>"
Set username for use with the TLS authentication method specified with
\fI--tlsauthtype\fP. Requires that \fI--tlspassword\fP also be set.  (Added in
7.21.4)
.IP "--tlspassword <password>"
Set password for use with the TLS authentication method specified with
\fI--tlsauthtype\fP. Requires that \fI--tlsuser\fP also be set.  (Added in
7.21.4)
.IP "--tr-encoding"
(HTTP) Request a compressed Transfer-Encoding response using one of the
algorithms curl supports, and uncompress the data while receiving it.

(Added in 7.21.6)
.IP "--trace <file>"
Enables a full trace dump of all incoming and outgoing data, including
descriptive information, to the given output file. Use "-" as filename to have
the output sent to stdout.

This option overrides previous uses of \fI-v, --verbose\fP or
\fI--trace-ascii\fP.

If this option is used several times, the last one will be used.
.IP "--trace-ascii <file>"
Enables a full trace dump of all incoming and outgoing data, including
descriptive information, to the given output file. Use "-" as filename to have
the output sent to stdout.

This is very 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.

This option overrides previous uses of \fI-v, --verbose\fP or \fI--trace\fP.

If this option is used several times, the last one will be used.
.IP "--trace-time"
Prepends a time stamp to each trace or verbose line that curl displays.
(Added in 7.14.0)
.IP "-u, --user <user:password>"
Specify the user name and password to use for server authentication. Overrides
\fI-n, --netrc\fP and \fI--netrc-optional\fP.

If you just give the user name (without entering a colon) curl will prompt for
a password.

If you use an SSPI-enabled curl binary and do NTLM authentication, you can
force curl to pick up the user name and password from your environment by
simply specifying a single colon with this option: "-u :".

If this option is used several times, the last one will be used.
.IP "-U, --proxy-user <user:password>"
Specify the user name and password to use for proxy authentication.

If you use an SSPI-enabled curl binary and do NTLM authentication, you can
force curl to pick up the user name and password from your environment by
simply specifying a single colon with this option: "-U :".

If this option is used several times, the last one will be used.
.IP "--url <URL>"
Specify a URL to fetch. This option is mostly handy when you want to specify
URL(s) in a config file.

This option may be used any number of times. To control where this URL is
written, use the \fI-o, --output\fP or the \fI-O, --remote-name\fP options.
.IP "-v, --verbose"
Makes the fetching more verbose/talkative. Mostly useful for debugging. 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.

Note that if you only want HTTP headers in the output, \fI-i, --include\fP
might be the option you're looking for.

If you think this option still doesn't give you enough details, consider using
\fI--trace\fP or \fI--trace-ascii\fP instead.

This option overrides previous uses of \fI--trace-ascii\fP or \fI--trace\fP.

Use \fI-s, --silent\fP to make curl quiet.
.IP "-w, --write-out <format>"
Defines what to display on stdout after a completed and successful
operation. The format is a string that may contain plain text mixed with any
number of variables. The string can be specified as "string", to get read from
a particular file you specify it "@filename" and to tell curl to read the
format from stdin you write "@-".

The variables present in the output format will be 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.

.B NOTE:
The %-symbol is a special symbol in the win32-environment, where all
occurrences of % must be doubled when using this option.

The variables available are:
.RS
.TP 15
.B content_type
The Content-Type of the requested document, if there was any.
.TP
.B filename_effective
The ultimate filename that curl writes out to. This is only meaningful if curl
is told to write to a file with the \fI--remote-name\fP or \fI--output\fP
option. It's most useful in combination with the \fI--remote-header-name\fP
option. (Added in 7.25.1)
.TP
.B ftp_entry_path
The initial path curl ended up in when logging on to the remote FTP
server. (Added in 7.15.4)
.TP
.B http_code
The numerical response code that was found in the last retrieved HTTP(S) or
FTP(s) transfer. In 7.18.2 the alias \fBresponse_code\fP was added to show the
same info.
.TP
.B http_connect
The numerical code that was found in the last response (from a proxy) to a
curl CONNECT request. (Added in 7.12.4)
.TP
.B local_ip
The IP address of the local end of the most recently done connection - can be
either IPv4 or IPv6 (Added in 7.29.0)
.TP
.B local_port
The local port number of the most recently done connection (Added in 7.29.0)
.TP
.B num_connects
Number of new connects made in the recent transfer. (Added in 7.12.3)
.TP
.B num_redirects
Number of redirects that were followed in the request. (Added in 7.12.3)
.TP
.B redirect_url
When an HTTP request was made without -L to follow redirects, this variable
will show the actual URL a redirect \fIwould\fP take you to. (Added in 7.18.2)
.TP
.B remote_ip
The remote IP address of the most recently done connection - can be either
IPv4 or IPv6 (Added in 7.29.0)
.TP
.B remote_port
The remote port number of the most recently done connection (Added in 7.29.0)
.TP
.B size_download
The total amount of bytes that were downloaded.
.TP
.B size_header
The total amount of bytes of the downloaded headers.
.TP
.B size_request
The total amount of bytes that were sent in the HTTP request.
.TP
.B size_upload
The total amount of bytes that were uploaded.
.TP
.B speed_download
The average download speed that curl measured for the complete download. Bytes
per second.
.TP
.B speed_upload
The average upload speed that curl measured for the complete upload. Bytes per
second.
.TP
.B ssl_verify_result
The result of the SSL peer certificate verification that was requested. 0
means the verification was successful. (Added in 7.19.0)
.TP
.B time_appconnect
The time, in seconds, it took from the start until the SSL/SSH/etc
connect/handshake to the remote host was completed. (Added in 7.19.0)
.TP
.B time_connect
The time, in seconds, it took from the start until the TCP connect to the
remote host (or proxy) was completed.
.TP
.B time_namelookup
The time, in seconds, it took from the start until the name resolving was
completed.
.TP
.B 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.
.TP
.B time_redirect
The time, in seconds, it took for all redirection steps include name lookup,
connect, pretransfer and transfer before the final transaction was
started. time_redirect shows the complete execution time for multiple
redirections. (Added in 7.12.3)
.TP
.B time_starttransfer
The time, in seconds, it took from the start until the first byte was just
about to be transferred. This includes time_pretransfer and also the time the
server needed to calculate the result.
.TP
.B time_total
The total time, in seconds, that the full operation lasted. The time will be
displayed with millisecond resolution.
.TP
.B url_effective
The URL that was fetched last. This is most meaningful if you've told curl
to follow location: headers.
.RE

If this option is used several times, the last one will be used.
.IP "-x, --proxy <[protocol://][user:password@]proxyhost[:port]>"
Use the specified proxy.

The proxy string can 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, http:// and all others will be treated as HTTP proxies. (The
protocol support was added in curl 7.21.7)

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's an environment variable setting a proxy, you can set proxy to
\&"" to override it.

All operations that are performed over an HTTP proxy will transparently be
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 exact same way as the proxy environment
variables, including the protocol prefix (http://) and the embedded user +
password.

If this option is used several times, the last one will be used.
.IP "-X, --request <command>"
(HTTP) Specifies a custom request method to use when communicating with the
HTTP server.  The specified request will be used instead of the method
otherwise used (which defaults to GET). Read the HTTP 1.1 specification for
details and explanations. Common additional HTTP requests include PUT and
DELETE, but related technologies like WebDAV offers PROPFIND, COPY, MOVE and
more.

Normally you don't need this option. All sorts of GET, HEAD, POST and PUT
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. So for example if you want to make a proper HEAD
request, using -X HEAD will not suffice. You need to use the \fI-I, --head\fP
option.

(FTP)
Specifies a custom FTP command to use instead of LIST when doing file lists
with FTP.

If this option is used several times, the last one will be used.

.IP "--xattr"
When saving output to a file, this option tells curl to store certain file
metadata in extended file attributes. Currently, 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.

.IP "-y, --speed-time <time>"
If a download is slower than speed-limit bytes per second during a speed-time
period, the download gets aborted. If speed-time is used, the default
speed-limit will be 1 unless set with \fI-Y\fP.

This option controls transfers and thus will not affect slow connects etc. If
this is a concern for you, try the \fI--connect-timeout\fP option.

If this option is used several times, the last one will be used.
.IP "-Y, --speed-limit <speed>"
If a download is slower than this given speed (in bytes per second) for
speed-time seconds it gets aborted. speed-time is set with \fI-y\fP and is 30
if not set.

If this option is used several times, the last one will be used.
.IP "-z, --time-cond <date expression>|<file>"
(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 doesn't match any internal ones, it
is taken as a filename and tries to get the modification date (mtime) from
<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 this option is used several times, the last one will be used.
.IP "-h, --help"
Usage help.
.IP "-M, --manual"
Manual. Display the huge help text.
.IP "-V, --version"
Displays 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.

The second line (starts with "Protocols:") shows all protocols that libcurl
reports to support.

The third line (starts with "Features:") shows specific features libcurl
reports to offer. Available features include:
.RS
.IP "IPv6"
You can use IPv6 with this.
.IP "krb4"
Krb4 for FTP is supported.
.IP "SSL"
HTTPS and FTPS are supported.
.IP "libz"
Automatic decompression of compressed files over HTTP is supported.
.IP "NTLM"
NTLM authentication is supported.
.IP "GSS-Negotiate"
Negotiate authentication and krb5 for FTP is supported.
.IP "Debug"
This curl uses a libcurl built with Debug. This enables more error-tracking
and memory debugging etc. For curl-developers only!
.IP "AsynchDNS"
This curl uses asynchronous name resolves.
.IP "SPNEGO"
SPNEGO Negotiate authentication is supported.
.IP "Largefile"
This curl supports transfers of large files, files larger than 2GB.
.IP "IDN"
This curl supports IDN - international domain names.
.IP "SSPI"
SSPI is supported. If you use NTLM and set a blank user name, curl will
authenticate with your current user and password.
.IP "TLS-SRP"
SRP (Secure Remote Password) authentication is supported for TLS.
.IP "Metalink"
This curl supports Metalink (both version 3 and 4 (RFC 5854)), which
describes mirrors and hashes.  curl will use mirrors for failover if
there are errors (such as the file or server not being available).
.RE
.SH FILES
.I ~/.curlrc
.RS
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--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>"
list of host names that shouldn't go through any proxy. If set to a asterisk
\&'*' only, it matches all hosts.
.SH "PROXY PROTOCOL PREFIXES"
Since curl version 7.21.7, 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 doesn't match
a supported one, the proxy will be treated as an HTTP proxy.

The supported proxy protocol prefixes are as follows:
.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 during bad conditions. At the time of this writing,
the exit codes are:
.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
Couldn't resolve proxy. The given proxy host could not be resolved.
.IP 6
Couldn't resolve host. The given remote host was not resolved.
.IP 7
Failed to connect to host.
.IP 8
FTP weird server reply. The server sent data curl couldn't 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 doesn't exist on the server.
.IP 11
FTP weird PASS reply. Curl couldn't parse the reply sent to the PASS request.
.IP 13
FTP weird PASV reply, Curl couldn't parse the reply sent to the PASV request.
.IP 14
FTP weird 227 format. Curl couldn't parse the 227-line the server sent.
.IP 15
FTP can't get host. Couldn't resolve the host IP we got in the 227-line.
.IP 17
FTP couldn't set binary. Couldn't change transfer method to binary.
.IP 18
Partial file. Only a part of the file was transferred.
.IP 19
FTP couldn't 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 couldn't write data to a local filesystem or similar.
.IP 25
FTP couldn't STOR file. The server denied the STOR operation, used for FTP
uploading.
.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 couldn't use REST. The REST command failed. This command is used for
resumed FTP transfers.
.IP 33
HTTP range error. The range "command" didn't work.
.IP 34
HTTP post error. Internal post-request generation error.
.IP 35
SSL connect error. The SSL handshaking failed.
.IP 36
FTP bad download resume. Couldn't continue an earlier aborted download.
.IP 37
FILE couldn't 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 51
The peer's SSL certificate or SSH MD5 fingerprint was not OK.
.IP 52
The server didn't 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
Couldn't use specified SSL cipher.
.IP 60
Peer certificate cannot be authenticated with known CA certificates.
.IP 61
Unrecognized transfer encoding.
.IP 62
Invalid LDAP URL.
.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 initialise SSL Engine.
.IP 67
The user name, 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 75
Character conversion failed.
.IP 76
Character conversion functions required.
.IP 77
Problem with 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 (added in 7.19.0).
.IP 83
Issuer check failed (added in 7.19.0).
.IP 84
The FTP PRET command failed
.IP 85
RTSP: mismatch of CSeq numbers
.IP 86
RTSP: mismatch of Session Identifiers
.IP 87
unable to parse FTP file list
.IP 88
FTP chunk callback reported error
.IP XX
More error codes will appear here in future releases. The existing ones
are meant to never change.
.SH AUTHORS / CONTRIBUTORS
Daniel Stenberg is the main author, but the whole list of contributors is
found in the separate THANKS file.
.SH WWW
http://curl.haxx.se
.SH FTP
ftp://ftp.sunet.se/pub/www/utilities/curl/
.SH "SEE ALSO"
.BR ftp (1),
.BR wget (1)