curl.1

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.TH curl 1 "28 November 2009" "Curl 7.21.4" "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 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
In general, all boolean options are enabled with --option 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 "-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 set more than once, the last one will be the one that's
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 "-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 set more than once, the last one will be the one that's
used.
.IP "-B/--use-ascii"
Enable ASCII transfer when using FTP or LDAP. 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 "--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://directory.fedora.redhat.com/docs/mod_nss.html#Directives\fP

If this option is used several times, the last one will override the others.
.IP "--compressed"
(HTTP) Request a compressed response using one of the algorithms libcurl
supports, and return 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. See also the \fI-m/--max-time\fP option.

If this option is used several times, the last one will be used.
.IP "-c/--cookie-jar <file name>"
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.

.B NOTE
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 "--create-dirs"
When used in conjunction with the -o option, curl will create the necessary
local directory hierarchy as needed. This option creates the dirs mentioned
with the -o option, nothing else. If the -o 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 @foobar\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
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 "--digest"
(HTTP) Enables HTTP Digest authentication. This is a authentication 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, the following occurrences make no
difference.
.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 EPRT 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 "-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 a 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 "-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 "--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 -w
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 "-E/--cert <certificate[:password]>"
(SSL) Tells curl to use the specified certificate file when getting a file
with HTTPS or FTPS. The certificate must be in PEM format.  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 this option is used several times, the last one will be used.
.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 then this option tells
curl the nickname of the CA 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 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. 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 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 a 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 "--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 twice, the second will override the previous use.
.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 a 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, the following occurrences make no
difference. 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-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-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 "--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) and that
can still be used but will be removed in a future version.
.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)
.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) and
that can still be used but will be removed in a future version.
.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 --ftp-ssl-ccc-mode 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 "-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

See further examples and details in the MANUAL.

This option can be used multiple times.
.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 a 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, the following occurrences make no
difference. This is because undoing a GET doesn't make sense, but you should
then instead enforce the alternative method you prefer.
.IP "-h/--help"
Usage help.
.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:".

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>"
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. This option is only for SCP
and SFTP transfers. (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 "--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 "-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 a FTP or FILE file, curl displays the file size and last modification
time only.
.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 -O/--remote-name 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 "--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 multiple times, the last occurrence sets the amount.
.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 "-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 "--libcurl <file>"
Append this option to any ordinary curl command line, and you will get a
libcurl-using source code written to the file that does the equivalent
of what your command-line operation does!

NOTE: this does not properly support -F and the sending of multipart
formposts, so in those cases the output program will be missing necessary
calls to \fIcurl_formadd(3)\fP, and possibly more.

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 "-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 "--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 "-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 "--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 "--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 "--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 "-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.  See also the \fI--connect-timeout\fP option.

If this option is used several times, the last one will be used.
.IP "-M/--manual"
Manual. Display the huge help text.
.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 "--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 -u/--user option to
activate the authentication code properly. Sending a '-u :' is enough as the
user name and password from the -u option aren't actually used.

If this option is used several times, the following occurrences make no
difference.
.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 "--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, the following occurrences make no
difference.
.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.

You may use this option as many times as the number of URLs you have.
.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 "--pass <phrase>"
(SSL/SSH) Passphrase for the private key

If this option is used several times, the last one will be used.
.IP "--post301"
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"
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 "--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),