Ubuntu Manpage: curl - transfer a URL

Provided by: curl_7.47.0-1ubuntu2.19_amd64

NAME

       curl - transfer a URL

SYNOPSIS

       curl [options] [URL...]

DESCRIPTION

       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, SMB, SMBS, 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 libcurl(3) for details.

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

When using [] or {} sequences when invoked from a command line prompt, you probably have
to put the full URL within double quotes to avoid the shell from interfering with it. This
also goes for other characters treated special, like for example '&', '?' and '*'.

Provide the IPv6 zone index in the URL with an escaped percentage sign and the interface
name. Like in

http://[fe80::3%25eth0]/

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 very 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.

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 disables 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, -# is your friend.

OPTIONS

Options start with one or two dashes. Many of the options require an additional value next
to them.

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 --option and yet again disabled with
--no-option. 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.)

-#, --progress-bar
Make curl display progress as a simple progress bar instead of the standard, more
informational, meter.

-:, --next
Tells curl to use a separate operation for the following URL and associated
options. This allows you to send several URL requests, each with their own specific
options, for example, such as different user names or custom requests for each.
(Added in 7.36.0)

-0, --http1.0
(HTTP) Tells curl to use HTTP version 1.0 instead of using its internally
preferred: HTTP 1.1.

--http1.1
(HTTP) Tells curl to use HTTP version 1.1. This is the internal default version.
(Added in 7.33.0)

--http2
(HTTP) Tells curl to issue its requests using HTTP 2. This requires that the
underlying libcurl was built to support it. (Added in 7.33.0)

--no-npn
Disable the NPN TLS extension. NPN is enabled by default if libcurl was built with
an SSL library that supports NPN. NPN is used by a libcurl that supports HTTP 2 to
negotiate HTTP 2 support with the server during https sessions.

(Added in 7.36.0)

--no-alpn
Disable the ALPN TLS extension. ALPN is enabled by default if libcurl was built
with an SSL library that supports ALPN. ALPN is used by a libcurl that supports
HTTP 2 to negotiate HTTP 2 support with the server during https sessions.

(Added in 7.36.0)

-1, --tlsv1
(SSL) Forces curl to use TLS version 1.x when negotiating with a remote TLS server.
You can use options --tlsv1.0, --tlsv1.1, and --tlsv1.2 to control the TLS version
more precisely (if the SSL backend in use supports such a level of control).

-2, --sslv2
(SSL) Forces curl to use SSL version 2 when negotiating with a remote SSL server.
Sometimes curl is built without SSLv2 support. SSLv2 is widely considered insecure
(see RFC 6176).

-3, --sslv3
(SSL) Forces curl to use SSL version 3 when negotiating with a remote SSL server.
Sometimes curl is built without SSLv3 support. SSLv3 is widely considered insecure
(see RFC 7568).

-4, --ipv4
This option tells curl to resolve names to IPv4 addresses only, and not for example
try IPv6.

-6, --ipv6
This option tells curl to resolve names to IPv6 addresses only, and not for example
try IPv4.

-a, --append
(FTP/SFTP) When used in an upload, this makes curl append to the target file
instead of overwriting it. If the remote file doesn't exist, it will be created.
Note that this flag is ignored by some SFTP servers (including OpenSSH).

-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 -H,
--header option of course.

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

--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 --basic, --digest, --ntlm, and --negotiate.

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.

-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 engine which will make curl
record incoming cookies too, which may be handy if you're using this in combination
with the -L, --location option. The file format of the file to read cookies from
should be plain HTTP headers or the Netscape/Mozilla cookie file format.

The file specified with -b, --cookie is only used as input. No cookies will be
written to the file. To store cookies, use the -c, --cookie-jar option.

Exercise caution if you are using this option and multiple transfers may occur. If
you use the NAME1=VALUE1; format, or in a file use the Set-Cookie format and don't
specify a domain, then the cookie is sent for any domain (even after redirects are
followed) and cannot be modified by a server-set cookie. If the cookie engine is
enabled and a server sets a cookie of the same name then both will be sent on a
future transfer to that server, likely not what you intended. To address these
issues set a domain in Set-Cookie (doing that will include sub-domains) or use the
Netscape format.

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

-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.

--basic
(HTTP) Tells curl to use HTTP Basic authentication with the remote host. 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 --ntlm,
--digest, or --negotiate).

Used together with -u, --user and -x, --proxy.

See also the -m, --max-time option.

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

--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 --ftp-create-dirs.

--crlf Convert LF to CRLF in upload. Useful for MVS (OS/390).

(SMTP added in 7.40.0)

--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)

-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 -F, --form.

-d, --data is the same as --data-ascii. --data-raw is almost the same but does not
have a special interpretation of the @ character. To post data purely binary, you
should instead use the --data-binary option. To URL-encode the value of a form
field you may use --data-urlencode.

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. Multiple files can
also be specified. Posting data from a file named 'foobar' would thus be done with
--data @foobar. When --data is told to read from a file like that, carriage returns
and newlines will be stripped out. If you don't want the @ character to have a
special interpretation use --data-raw instead.

-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 -b, --cookie option! The -c, --cookie-jar option is 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.

--data-ascii <data>
See -d, --data.

--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 --data-ascii 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 -d, --data.

--data-raw <data>
(HTTP) This posts data similarly to --data but without the special interpretation
of the @ character. See -d, --data. (Added in 7.43.0)

--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 name followed by a
separator and a content specification. The <data> part can be passed to curl using
one of the following syntaxes:

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!

=content
This will make curl URL-encode the content and pass that on. The preceding =
symbol is not included in the data.

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.

@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.

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 name=urlencoded-file-content. Note that the name
is expected to be URL-encoded already.

--delegation LEVEL
Set LEVEL to tell the server what it is allowed to delegate when it comes to user
credentials. Used with GSS/kerberos.

none Don't allow any delegation.

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.

always Unconditionally allow the server to delegate.

--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 -u, --user option to set user name and password. See
also --ntlm, --negotiate and --anyauth for related options.

If this option is used several times, only the first one is used.

--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.

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

Disabling EPRT only changes the active behavior. If you want to switch to passive
mode you need to not use -P, --ftp-port or force it with --ftp-pasv.

--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.

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

Disabling EPSV only changes the passive behavior. If you want to switch to active
mode you need to use -P, --ftp-port.

--dns-interface <interface>
Tell curl to send outgoing DNS requests through <interface>. This option is a
counterpart to --interface (which does not affect DNS). The supplied string must be
an interface name (not an address).

This option requires that libcurl was built with a resolver backend that supports
this operation. The c-ares backend is the only such one. (Added in 7.33.0)

--dns-ipv4-addr <ip-address>
Tell curl to bind to <ip-address> when making IPv4 DNS requests, so that the DNS
requests originate from this address. The argument should be a single IPv4 address.

This option requires that libcurl was built with a resolver backend that supports
this operation. The c-ares backend is the only such one. (Added in 7.33.0)

--dns-ipv6-addr <ip-address>
Tell curl to bind to <ip-address> when making IPv6 DNS requests, so that the DNS
requests originate from this address. The argument should be a single IPv6 address.

This option requires that libcurl was built with a resolver backend that supports
this operation. The c-ares backend is the only such one. (Added in 7.33.0)

--dns-servers <ip-address,ip-address>
Set the list of DNS servers to be used instead of the system default. The list of
IP addresses should be separated with commas. Port numbers may also optionally be
given as :<port-number> after each IP address.

This option requires that libcurl was built with a resolver backend that supports
this operation. The c-ares backend is the only such one. (Added in 7.33.0)

-e, --referer <URL>
(HTTP) Sends the "Referrer Page" information to the HTTP server. This can also be
set with the -H, --header flag of course. When used with -L, --location 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.

-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
client certificate concatenated! See --cert and --key 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.

--engine <name>
Select the OpenSSL crypto engine to use for cipher operations. Use --engine list to
print a list of build-time supported engines. Note that not all (or none) of the
engines may be available at run-time.

--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.

--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 --random-file
option.

--expect100-timeout <seconds>
(HTTP) Maximum time in seconds that you allow curl to wait for a 100-continue
response when curl emits an Expects: 100-continue header in its request. By default
curl will wait one second. This option accepts decimal values! When curl stops
waiting, it will continue as if the response has been received.

(Added in 7.47.0)

--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.

--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.

--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 --capath can allow OpenSSL-powered curl to make SSL-
connections much more efficiently than using --cacert if the --cacert 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.

--pinnedpubkey <pinned public key (hashes)>
(SSL) Tells curl to use the specified public key file (or hashes) to verify the
peer. This can be a path to a file which contains a single public key in PEM or DER
format, or any number of base64 encoded sha256 hashes preceded by ´sha256//´ and
separated by ´;´

When negotiating a TLS or SSL connection, the server sends a certificate indicating
its identity. A public key is extracted from this certificate and if it does not
exactly match the public key provided to this option, curl will abort the
connection before sending or receiving any data.

Added in 7.39.0 for OpenSSL, GnuTLS and GSKit. Added in 7.43.0 for NSS and
wolfSSL/CyaSSL. sha256 support added in 7.44.0 for OpenSSL, GnuTLS, NSS and
wolfSSL/CyaSSL. Other SSL backends not supported.

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

--cert-status
(SSL) Tells curl to verify the status of the server certificate by using the
Certificate Status Request (aka. OCSP stapling) TLS extension.

If this option is enabled and the server sends an invalid (e.g. expired) response,
if the response suggests that the server certificate has been revoked, or no
response at all is received, the verification fails.

This is currently only implemented in the OpenSSL, GnuTLS and NSS backends. (Added
in 7.41.0)

--false-start

(SSL) Tells curl to use false start during the TLS handshake. False start is a mode
where a TLS client will start sending application data before verifying the
server's Finished message, thus saving a round trip when performing a full
handshake.

This is currently only implemented in the NSS and Secure Transport (on iOS 7.0 or
later, or OS X 10.9 or later) backends. (Added in 7.42.0)

-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).

-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:

curl -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. Unfortunately it does not support reading the file from a
named pipe or similar, as it needs the full size before the transfer starts.

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

curl -F "web=@index.html;type=text/html" url.com

curl -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:

curl -F "file=@localfile;filename=nameinpost" url.com

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

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

curl -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.

--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.

--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)

--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.

--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:

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.

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.

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'.

(Added in 7.15.1)

--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 -P/-ftp-port
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
-P, --ftp-port again.

Passive mode means that curl will try the EPSV command first and then PASV, unless
--disable-epsv is used.

--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.

--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)

--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)

--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)

--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.

--form-string <name=string>
(HTTP) Similar to --form 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 --form if there's any
possibility that the string value may accidentally trigger the '@' or '<' features
of --form.

-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.

-G, --get
When used, this option will make all data specified with -d, --data, --data-binary
or --data-urlencode 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.

-H, --header <header>
(HTTP) Extra header to include in the request when sending HTTP to a server. 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 not 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 -A, --user-agent and -e, --referer options.

Starting in 7.37.0, you need --proxy-header to send custom headers intended for a
proxy.

Example:

# curl -H "X-First-Name: Joe" http://192.168.0.1/

WARNING: headers set with this option will be set in all requests - even after
redirects are followed, like when told with -L, --location. This can lead to the
header being sent to other hosts than the original host, so sensitive headers
should be used with caution combined with following redirects.

This option can be used multiple times to add/replace/remove multiple headers.

--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)

--ignore-content-length
For 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.

For FTP (since 7.46.0), skip the RETR command to figure out the size before
downloading a file.

-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...

-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.

--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.

-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.

-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.

There's no attempt to decode %-sequences (yet) in the provided file name, so this
option may provide you with rather unexpected file names.

-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 -k, --insecure is used.

See this online resource for further details:
http://curl.haxx.se/docs/sslcerts.html

-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, or the equals sign. Long option names can
optionally be given in the config file without the initial double dashes and if so,
the colon or equals characters can be used as separators. If the option is
specified with one or two dashes, there can be no colon or equals character between
the option and its parameter.

If the parameter 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 --url 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/"

When curl is invoked, it always (unless -q 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.

# --- 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 ---

This option can be used multiple times to load multiple config files.

--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
--no-keepalive 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.

--key <key>
(SSL/SSH) Private key file name. Allows you to provide your private key in this
separate file. For SSH, if not specified, curl tries the following candidates in
order: '~/.ssh/id_rsa', '~/.ssh/id_dsa', './id_rsa', './id_dsa'.

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

--key-type <type>
(SSL) Private key file type. Specify which type your --key 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.

--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 support. This is not very
common. Use -V, --version to see if your curl supports it.

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

-l, --list-only
(FTP) When listing an FTP directory, this switch forces a name-only view. This is
especially useful if the user wants to machine-parse the contents of an FTP
directory since the normal directory view doesn't use a standard look or format.
When used like this, the option causes a NLST command to be sent to the server
instead of LIST.

Note: Some FTP servers list only files in their response to NLST; they do not
include sub-directories and symbolic links.

(POP3) When retrieving a specific email from POP3, this switch forces a LIST
command to be performed instead of RETR. This is particularly useful if the user
wants to see if a specific message id exists on the server and what size it is.

Note: When combined with -X, --request <command>, this option can be used to send
an UIDL command instead, so the user may use the email's unique identifier rather
than it's message id to make the request. (Added in 7.21.5)

-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 -i,
--include or -I, --head, 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 --location-trusted on how to change this. You can limit the
amount of redirects to follow by using the --max-redirs 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.

You can tell curl to not change the non-GET request method to GET after a 30x
response by using the dedicated options for that: --post301, --post302 and
-post303.

--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)

--limit-rate <speed>
Specify the maximum transfer rate you want curl to use - for both downloads and
uploads. This feature is useful if you have a limited pipe and you'd like your
transfer not to use your entire bandwidth. To make it slower than it otherwise
would be.

The given speed is measured in bytes/second, unless a suffix is appended.
Appending '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 -Y, --speed-limit 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.

--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)

--location-trusted
(HTTP/HTTPS) Like -L, --location, 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).

-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 --connect-timeout option.

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

--login-options <options>
Specify the login options to use during server authentication.

You can use the login options to specify protocol specific options that may be used
during authentication. At present only IMAP, POP3 and SMTP support login options.
For more information about the login options please see RFC 2384, RFC 5092 and IETF
draft draft-earhart-url-smtp-00.txt (Added in 7.34.0).

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

--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)

--mail-from <address>
(SMTP) Specify a single address that the given mail should get sent from.

(Added in 7.20.0)

--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.

NOTE: 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.

--mail-rcpt <address>
(SMTP) Specify a single address, user name or mailing list name.

When performing a mail transfer, the recipient should specify a valid email address
to send the mail to. (Added in 7.20.0)

When performing an address verification (VRFY command), the recipient should be
specified as the user name or user name and domain (as per Section 3.5 of RFC5321).
(Added in 7.34.0)

When performing a mailing list expand (EXPN command), the recipient should be
specified using the mailing list name, such as "Friends" or "London-Office".
(Added in 7.34.0)

--max-redirs <num>
Set maximum number of redirection-followings allowed. If -L, --location 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.

--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:

curl --metalink http://www.example.com/example.metalink

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

curl --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 --metalink and
--include are used together, --include 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.)

-n, --netrc
Makes curl scan the .netrc (_netrc 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 netrc(5) 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 .netrc to allow curl to FTP to
the machine host.domain.com with user name 'myself' and password 'secret' should
look similar to:

machine host.domain.com login myself password secret

-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 --buffer to
enforce the buffering.

--netrc-file
This option is similar to --netrc, 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 --netrc-file options are provided, only the last
one will be used. (Added in 7.21.5)

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

--netrc-optional
Very similar to --netrc, but this option makes the .netrc usage optional and not
mandatory as the --netrc option does.

--negotiate
(HTTP) Enables Negotiate (SPNEGO) authentication.

If you want to enable Negotiate (SPNEGO) for proxy authentication, then use
--proxy-negotiate.

This option requires a library built with GSS-API or SSPI support. Use -V,
--version to see if your curl supports GSS-API/SSPI and SPNEGO.

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, only the first one is used.

--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 --keepalive
to enforce keepalive.

--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 --sessionid
to enforce session-ID caching.

--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).

--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 --proxy-ntlm.

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

If this option is used several times, only the first one is used.

-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 --create-dirs option to create the local directories dynamically.
Specifying the output as '-' (a single dash) will force the output to be done to
stdout.

-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 -O, --remote-name flag!

There is no URL decoding done on the file name. If it has %20 or other URL encoded
parts of the name, they will end up as-is as file name.

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

--oauth2-bearer
(IMAP, POP3, SMTP) Specify the Bearer Token for OAUTH 2.0 server authentication.
The Bearer Token is used in conjunction with the user name which can be specified
as part of the --url or -u, --user options.

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.

--proxy-header <header>
(HTTP) Extra header to include in the request when sending HTTP to a proxy. You may
specify any number of extra headers. This is the equivalent option to -H, --header
but is for proxy communication only like in CONNECT requests when you want a
separate header sent to the proxy to what is sent to the actual remote host.

Headers specified with this option will not be included in requests that curl knows
will not be sent to a proxy.

This option can be used multiple times to add/replace/remove multiple headers.

(Added in 7.37.0)

-p, --proxytunnel
When an HTTP proxy is used (-x, --proxy), 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.

-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:

interface
i.e "eth0" to specify which interface's IP address you want to use (Unix
only)

IP address
i.e "192.168.10.1" to specify the exact IP address

host name
i.e "my.host.domain" to specify the machine

- make curl pick the same IP address that is already used for the control
connection

If this option is used several times, the last one will be used. Disable the use of
PORT with --ftp-pasv. Disable the attempt to use the EPRT command instead of PORT
by using --disable-eprt. 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.

--pass <phrase>
(SSL/SSH) Passphrase for the private key

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

--path-as-is
Tell curl to not handle sequences of /../ or /./ in the given URL path. Normally
curl will squash or merge them according to standards but with this option set you
tell it not to do that.

(Added in 7.42.0)

--post301
(HTTP) Tells curl to respect RFC 7230/6.4.2 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 -L, --location (Added in 7.17.1)

--post302
(HTTP) Tells curl to respect RFC 7230/6.4.3 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 -L, --location (Added in 7.19.1)

--post303
(HTTP) Tells curl to respect RFC 7230/6.4.4 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 -L, --location (Added in 7.26.0)

--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:

+ Permit this protocol in addition to protocols already permitted (this is the
default if no modifier is used).

- Deny this protocol, removing it from the list of protocols already permitted.

= Permit only this protocol (ignoring the list already permitted), though subject
to later modification by subsequent entries in the comma separated list.

For example:

--proto -ftps uses the default protocols, but disables ftps

--proto -all,https,+http
only enables http and https

--proto =http,https
also only enables http and https

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)

--proto-default <protocol>
Tells curl to use protocol for any URL missing a scheme name.

Example:

--proto-default https ftp.mozilla.org
https://ftp.mozilla.org

An unknown or unsupported protocol causes error CURLE_UNSUPPORTED_PROTOCOL.

This option does not change the default proxy protocol (http).

Without this option curl would make a guess based on the host, see --url for details.

(Added in 7.45.0)

--proto-redir <protocols>
Tells curl to use the listed protocols on redirect. See --proto for how protocols
are represented.

Example:

--proto-redir -all,http,https
Allow only HTTP and HTTPS on redirect.

By default curl will allow all protocols on redirect except several disabled for security
reasons: Since 7.19.4 FILE and SCP are disabled, and since 7.40.0 SMB and SMBS are also
disabled. Specifying all or +all enables all protocols on redirect, including those
disabled for security.

(Added in 7.20.2)

--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)

--proxy-basic
Tells curl to use HTTP Basic authentication when communicating with the given
proxy. Use --basic for enabling HTTP Basic with a remote host. Basic is the default
authentication method curl uses with proxies.

--proxy-digest
Tells curl to use HTTP Digest authentication when communicating with the given
proxy. Use --digest for enabling HTTP Digest with a remote host.

--proxy-negotiate
Tells curl to use HTTP Negotiate (SPNEGO) authentication when communicating with
the given proxy. Use --negotiate for enabling HTTP Negotiate (SPNEGO) with a remote
host. (Added in 7.17.1)

--proxy-ntlm
Tells curl to use HTTP NTLM authentication when communicating with the given proxy.
Use --ntlm for enabling NTLM with a remote host.

--proxy-service-name <servicename>
This option allows you to change the service name for proxy negotiation.

Examples: --proxy-negotiate proxy-name --proxy-service-name sockd would use
sockd/proxy-name. (Added in 7.43.0).

--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 (-x, --proxy), is that
attempts to use CONNECT through the proxy will specify an HTTP 1.0 protocol instead
of the default HTTP 1.1.

--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.

(As of 7.39.0, curl attempts to automatically extract the public key from the
private key file, so passing this option is generally not required. Note that this
public key extraction requires libcurl to be linked against a copy of libssh2 1.2.8
or higher that is itself linked against OpenSSL.)

-q If used as the first parameter on the command line, the curlrc config file will not
be read and used. See the -K, --config for details on the default config file
search path.

-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:

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.

chmod mode file
The chmod command modifies the file mode bits of the specified file. The
mode operand is an octal integer mode number.

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.

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.

mkdir directory_name
The mkdir command creates the directory named by the directory_name operand.

pwd The pwd command returns the absolute pathname of the current working
directory.

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.

rm file
The rm command removes the file specified by the file operand.

rmdir directory
The rmdir command removes the directory entry specified by the directory
operand, provided it is empty.

symlink source_file target_file
See ln.

-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.

0-499 specifies the first 500 bytes

500-999 specifies the second 500 bytes

-500 specifies the last 500 bytes

9500- specifies the bytes from offset 9500 and forward

0-0,-1 specifies the first and last byte only(*)(HTTP)

100-199,500-599
specifies two separate 100-byte ranges(*) (HTTP)

(*) = 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.

-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.

--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
--egd-file option.

--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)

--remote-name-all
This option changes the default action for all given URLs to be dealt with as if
-O, --remote-name were used for each one. So if you want to disable that for a
specific URL after --remote-name-all has been used, you must use "-o -" or --no-
remote-name. (Added in 7.19.0)

--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)

--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 --retry-
delay you disable this exponential backoff algorithm. See also --retry-max-time 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.

--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 --retry 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.

--retry-max-time <seconds>
The retry timer is reset before the first transfer attempt. Retries will be done as
usual (see --retry) 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 -m, --max-time. 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.

-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.

--sasl-ir
Enable initial response in SASL authentication. (Added in 7.31.0)

--service-name <servicename>
This option allows you to change the service name for SPNEGO.

Examples: --negotiate --service-name sockd would use sockd/server-name. (Added in
7.43.0).

-S, --show-error
When used with -s it makes curl show an error message if it fails.

--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 --ftp-ssl-
control and --ssl-reqd for different levels of encryption required. (Added in
7.20.0)

This option was formerly known as --ftp-ssl (Added in 7.11.0). That option name can
still be used but will be removed in a future version.

--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 --ftp-ssl-reqd (added in 7.15.5). That option
name can still be used but will be removed in a future version.

--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
workarounds 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)

--ssl-no-revoke
(WinSSL) This option tells curl to disable certificate revocation checks. WARNING:
this option loosens the SSL security, and by using this flag you ask for exactly
that. (Added in 7.44.0)

--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 -x, --proxy, as they are mutually
exclusive.

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

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

--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 -x, --proxy, as they are mutually
exclusive.

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

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

--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 -x, --proxy, as they are mutually
exclusive.

Since 7.21.7, this option is superfluous since you can specify a socks5 hostname
proxy with -x, --proxy 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.)

--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 -x, --proxy, as they are mutually
exclusive.

Since 7.21.7, this option is superfluous since you can specify a socks5 proxy with
-x, --proxy 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 --socks4) does not work with IPV6, FTPS or LDAP.

--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 --socks5-gssapi-service sockd would use sockd/proxy-
name --socks5 proxy-name --socks5-gssapi-service 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).

--socks5-gssapi-nec
As part of the GSS-API negotiation a protection mode is negotiated. RFC 1961 says
in section 4.3/4.4 it should be protected, but the NEC reference implementation
does not. The option --socks5-gssapi-nec allows the unprotected exchange of the
protection mode negotiation. (Added in 7.19.4).

--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.

-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.

-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/

--tcp-nodelay
Turn on the TCP_NODELAY option. See the curl_easy_setopt(3) man page for details
about this option. (Added in 7.11.2)

--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)

--tlsauthtype <authtype>
Set TLS authentication type. Currently, the only supported option is "SRP", for
TLS-SRP (RFC 5054). If --tlsuser and --tlspassword are specified but --tlsauthtype
is not, then this option defaults to "SRP". (Added in 7.21.4)

--tlspassword <password>
Set password for use with the TLS authentication method specified with
--tlsauthtype. Requires that --tlsuser also be set. (Added in 7.21.4)

--tlsuser <user>
Set username for use with the TLS authentication method specified with
--tlsauthtype. Requires that --tlspassword also be set. (Added in 7.21.4)

--tlsv1.0
(SSL) Forces curl to use TLS version 1.0 when negotiating with a remote TLS server.
(Added in 7.34.0)

--tlsv1.1
(SSL) Forces curl to use TLS version 1.1 when negotiating with a remote TLS server.
(Added in 7.34.0)

--tlsv1.2
(SSL) Forces curl to use TLS version 1.2 when negotiating with a remote TLS server.
(Added in 7.34.0)

--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)

--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 -v, --verbose or --trace-ascii.

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

--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 --trace, 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 -v, --verbose or --trace.

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

--trace-time
Prepends a time stamp to each trace or verbose line that curl displays. (Added in
7.14.0)

--unix-socket <path>
(HTTP) Connect through this Unix domain socket, instead of using the network.
(Added in 7.40.0)

-u, --user <user:password>
Specify the user name and password to use for server authentication. Overrides -n,
--netrc and --netrc-optional.

If you simply specify the user name, curl will prompt for a password.

The user name and passwords are split up on the first colon, which makes it
impossible to use a colon in the user name with this option. The password can,
still.

When using Kerberos V5 with a Windows based server you should include the Windows
domain name in the user name, in order for the server to successfully obtain a
Kerberos Ticket. If you don't then the initial authentication handshake may fail.

When using NTLM, the user name can be specified simply as the user name, without
the domain, if there is a single domain and forest in your setup for example.

To specify the domain name use either Down-Level Logon Name or UPN (User Principal
Name) formats. For example, EXAMPLE\user and user@example.com respectively.

If you use a Windows SSPI-enabled curl binary and perform Kerberos V5, Negotiate,
NTLM or Digest authentication then you can tell curl to select the user name and
password from your environment by specifying a single colon with this option: "-u
:".

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

-U, --proxy-user <user:password>
Specify the user name and password to use for proxy authentication.

If you use a Windows SSPI-enabled curl binary and do either Negotiate or NTLM
authentication then you can tell curl to select the user name and password from
your environment by specifying a single colon with this option: "-U :".

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

--url <URL>
Specify a URL to fetch. This option is mostly handy when you want to specify URL(s)
in a config file.

If the given URL is missing a scheme name (such as "http://" or "ftp://" etc) then
curl will make a guess based on the host. If the outermost sub-domain name matches
DICT, FTP, IMAP, LDAP, POP3 or SMTP then that protocol will be used, otherwise HTTP
will be used. Since 7.45.0 guessing can be disabled by setting a default protocol,
see --proto-default for details.

This option may be used any number of times. To control where this URL is written,
use the -o, --output or the -O, --remote-name options.

-v, --verbose
Be more verbose/talkative during the operation. Useful for debugging and seeing
what's going on "under the hood". A line starting with '>' means "header data" sent
by curl, '<' means "header data" received by curl that is hidden in normal cases,
and a line starting with '*' means additional info provided by curl.

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

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

This option overrides previous uses of --trace-ascii or --trace.

Use -s, --silent to make curl quiet.

-w, --write-out <format>
Make curl display information on stdout after a completed transfer. The format is a
string that may contain plain text mixed with any number of variables. The format
can be specified as a literal "string", or you can have curl read the format from a
file with "@filename" and to tell curl to read the format from stdin you write
"@-".

The variables present in the output format 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.

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:

content_type The Content-Type of the requested document, if there was any.

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 --remote-name
or --output option. It's most useful in combination with the
--remote-header-name option. (Added in 7.25.1)

ftp_entry_path The initial path curl ended up in when logging on to the remote FTP
server. (Added in 7.15.4)

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 response_code was
added to show the same info.

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)

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)

local_port The local port number of the most recently done connection (Added in
7.29.0)

num_connects Number of new connects made in the recent transfer. (Added in
7.12.3)

num_redirects Number of redirects that were followed in the request. (Added in
7.12.3)

redirect_url When an HTTP request was made without -L to follow redirects, this
variable will show the actual URL a redirect would take you to.
(Added in 7.18.2)

remote_ip The remote IP address of the most recently done connection - can be
either IPv4 or IPv6 (Added in 7.29.0)

remote_port The remote port number of the most recently done connection (Added
in 7.29.0)

size_download The total amount of bytes that were downloaded.

size_header The total amount of bytes of the downloaded headers.

size_request The total amount of bytes that were sent in the HTTP request.

size_upload The total amount of bytes that were uploaded.

speed_download The average download speed that curl measured for the complete
download. Bytes per second.

speed_upload The average upload speed that curl measured for the complete upload.
Bytes per second.

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)

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)

time_connect The time, in seconds, it took from the start until the TCP connect
to the remote host (or proxy) was completed.

time_namelookup
The time, in seconds, it took from the start until the name
resolving was completed.

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.

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)

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.

time_total The total time, in seconds, that the full operation lasted. The time
will be displayed with millisecond resolution.

url_effective The URL that was fetched last. This is most meaningful if you've
told curl to follow location: headers.

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

-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 -p, --proxytunnel 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.

-X, --request <command>
(HTTP) Specifies a custom request method to use when communicating with the HTTP
server. The specified request method 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 -I, --head option.

The method string you set with -X will be used for all requests, which if you for
example use -L, --location may cause unintended side-effects when curl doesn't
change request method according to the HTTP 30x response codes - and similar.

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

(POP3) Specifies a custom POP3 command to use instead of LIST or RETR. (Added in
7.26.0)

(IMAP) Specifies a custom IMAP command to use instead of LIST. (Added in 7.30.0)

(SMTP) Specifies a custom SMTP command to use instead of HELP or VRFY. (Added in
7.34.0)

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

--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.

-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 -Y.

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

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

-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 -y and is 30 if not set.

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

-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 curl_getdate(3) 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.

-h, --help
Usage help. This lists all current command line options with a short description.

-M, --manual
Manual. Display the huge help text.

-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:

IPv6 You can use IPv6 with this.

krb4 Krb4 for FTP is supported.

SSL SSL versions of various protocols are supported, such as HTTPS, FTPS, POP3S
and so on.

libz Automatic decompression of compressed files over HTTP is supported.

NTLM NTLM authentication is supported.

Debug This curl uses a libcurl built with Debug. This enables more error-tracking
and memory debugging etc. For curl-developers only!

AsynchDNS
This curl uses asynchronous name resolves. Asynchronous name resolves can be
done using either the c-ares or the threaded resolver backends.

SPNEGO SPNEGO authentication is supported.

Largefile
This curl supports transfers of large files, files larger than 2GB.

IDN This curl supports IDN - international domain names.

GSS-API
GSS-API is supported.

SSPI SSPI is supported.

TLS-SRP
SRP (Secure Remote Password) authentication is supported for TLS.

HTTP2 HTTP/2 support has been built-in.

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).

FILES

       ~/.curlrc
              Default config file, see -K, --config for details.

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  --proxy
       option.

       http_proxy [protocol://]<host>[:port]
              Sets the proxy server to use for HTTP.

       HTTPS_PROXY [protocol://]<host>[:port]
              Sets the proxy server to use for HTTPS.

       [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.

       ALL_PROXY [protocol://]<host>[:port]
              Sets the proxy server to use if no protocol-specific proxy is set.

       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.

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:

       socks4://
              Makes it the equivalent of --socks4

       socks4a://
              Makes it the equivalent of --socks4a

       socks5://
              Makes it the equivalent of --socks5

       socks5h://
              Makes it the equivalent of --socks5-hostname

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:

1 Unsupported protocol. This build of curl has no support for this protocol.

2 Failed to initialize.

3 URL malformed. The syntax was not correct.

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!

5 Couldn't resolve proxy. The given proxy host could not be resolved.

6 Couldn't resolve host. The given remote host was not resolved.

7 Failed to connect to host.

8 FTP weird server reply. The server sent data curl couldn't parse.

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.

11 FTP weird PASS reply. Curl couldn't parse the reply sent to the PASS request.

13 FTP weird PASV reply, Curl couldn't parse the reply sent to the PASV request.

14 FTP weird 227 format. Curl couldn't parse the 227-line the server sent.

15 FTP can't get host. Couldn't resolve the host IP we got in the 227-line.

17 FTP couldn't set binary. Couldn't change transfer method to binary.

18 Partial file. Only a part of the file was transferred.

19 FTP couldn't download/access the given file, the RETR (or similar) command failed.

21 FTP quote error. A quote command returned error from the server.

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 -f,
--fail is used.

23 Write error. Curl couldn't write data to a local filesystem or similar.

25 FTP couldn't STOR file. The server denied the STOR operation, used for FTP
uploading.

26 Read error. Various reading problems.

27 Out of memory. A memory allocation request failed.

28 Operation timeout. The specified time-out period was reached according to the
conditions.

30 FTP PORT failed. The PORT command failed. Not all FTP servers support the PORT
command, try doing a transfer using PASV instead!

31 FTP couldn't use REST. The REST command failed. This command is used for resumed
FTP transfers.

33 HTTP range error. The range "command" didn't work.

34 HTTP post error. Internal post-request generation error.

35 SSL connect error. The SSL handshaking failed.

36 FTP bad download resume. Couldn't continue an earlier aborted download.

37 FILE couldn't read file. Failed to open the file. Permissions?

38 LDAP cannot bind. LDAP bind operation failed.

39 LDAP search failed.

41 Function not found. A required LDAP function was not found.

42 Aborted by callback. An application told curl to abort the operation.

43 Internal error. A function was called with a bad parameter.

45 Interface error. A specified outgoing interface could not be used.

47 Too many redirects. When following redirects, curl hit the maximum amount.

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!

49 Malformed telnet option.

51 The peer's SSL certificate or SSH MD5 fingerprint was not OK.

52 The server didn't reply anything, which here is considered an error.

53 SSL crypto engine not found.

54 Cannot set SSL crypto engine as default.

55 Failed sending network data.

56 Failure in receiving network data.

58 Problem with the local certificate.

59 Couldn't use specified SSL cipher.

60 Peer certificate cannot be authenticated with known CA certificates.

61 Unrecognized transfer encoding.

62 Invalid LDAP URL.

63 Maximum file size exceeded.

64 Requested FTP SSL level failed.

65 Sending the data requires a rewind that failed.

66 Failed to initialise SSL Engine.

67 The user name, password, or similar was not accepted and curl failed to log in.

68 File not found on TFTP server.

69 Permission problem on TFTP server.

70 Out of disk space on TFTP server.

71 Illegal TFTP operation.

72 Unknown TFTP transfer ID.

73 File already exists (TFTP).

74 No such user (TFTP).

75 Character conversion failed.

76 Character conversion functions required.

77 Problem with reading the SSL CA cert (path? access rights?).

78 The resource referenced in the URL does not exist.

79 An unspecified error occurred during the SSH session.

80 Failed to shut down the SSL connection.

82 Could not load CRL file, missing or wrong format (added in 7.19.0).

83 Issuer check failed (added in 7.19.0).

84 The FTP PRET command failed

85 RTSP: mismatch of CSeq numbers

86 RTSP: mismatch of Session Identifiers

87 unable to parse FTP file list

88 FTP chunk callback reported error

89 No connection available, the session will be queued

90 SSL public key does not matched pinned public key

XX More error codes will appear here in future releases. The existing ones are meant
to never change.

AUTHORS / CONTRIBUTORS

       Daniel  Stenberg  is  the  main author, but the whole list of contributors is found in the
       separate THANKS file.

WWW

       http://curl.haxx.se

FTP

       ftp://ftp.sunet.se/pub/www/utilities/curl/

NAME

SYNOPSIS

DESCRIPTION

URL

PROGRESS METER

OPTIONS

FILES

ENVIRONMENT

PROXY PROTOCOL PREFIXES

EXIT CODES

AUTHORS / CONTRIBUTORS

WWW

FTP

SEE ALSO