curl_easy_setopt.3

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.IP CURLOPT_NETRC
This parameter controls the preference of libcurl between using user names and
passwords from your \fI~/.netrc\fP file, relative to user names and passwords
in the URL supplied with \fICURLOPT_URL\fP.

libcurl uses a user name (and supplied or prompted password) supplied with
\fICURLOPT_USERPWD\fP in preference to any of the options controlled by this
parameter.

Pass a long, set to one of the values described below.
.RS
.IP CURL_NETRC_OPTIONAL
The use of your \fI~/.netrc\fP file is optional,
and information in the URL is to be preferred.  The file will be scanned
with the host and user name (to find the password only) or with the host only,
to find the first user name and password after that \fImachine\fP,
which ever information is not specified in the URL.

Undefined values of the option will have this effect.
.IP CURL_NETRC_IGNORED
The library will ignore the file and use only the information in the URL.

This is the default.
.IP CURL_NETRC_REQUIRED
This value tells the library that use of the file is required,
to ignore the information in the URL,
and to search the file with the host only.
.RE
Only machine name, user name and password are taken into account
(init macros and similar things aren't supported).

libcurl does not verify that the file has the correct properties set (as the
standard Unix ftp client does). It should only be readable by user.
.IP CURLOPT_NETRC_FILE
Pass a char * as parameter, pointing to a zero terminated string containing
the full path name to the file you want libcurl to use as .netrc file. If this
option is omitted, and \fICURLOPT_NETRC\fP is set, libcurl will attempt to
find the a .netrc file in the current user's home directory. (Added in 7.10.9)
.IP CURLOPT_USERPWD
Pass a char * as parameter, which should be [user name]:[password] to use for
the connection. Use \fICURLOPT_HTTPAUTH\fP to decide authentication method.

When using NTLM, you can set domain by prepending it to the user name and
separating the domain and name with a forward (/) or backward slash (\\). Like
this: "domain/user:password" or "domain\\user:password". Some HTTP servers (on
Windows) support this style even for Basic authentication.

When using HTTP and \fICURLOPT_FOLLOWLOCATION\fP, libcurl might perform
several requests to possibly different hosts. libcurl will only send this user
and password information to hosts using the initial host name (unless
\fICURLOPT_UNRESTRICTED_AUTH\fP is set), so if libcurl follows locations to
other hosts it will not send the user and password to those. This is enforced
to prevent accidental information leakage.
.IP CURLOPT_PROXYUSERPWD
Pass a char * as parameter, which should be [user name]:[password] to use for
the connection to the HTTP proxy.  Use \fICURLOPT_PROXYAUTH\fP to decide
authentication method.
.IP CURLOPT_HTTPAUTH
Pass a long as parameter, which is set to a bitmask, to tell libcurl what
authentication method(s) you want it to use. The available bits are listed
below. If more than one bit is set, libcurl will first query the site to see
what authentication methods it supports and then pick the best one you allow
it to use. For some methods, this will induce an extra network round-trip. Set
the actual name and password with the \fICURLOPT_USERPWD\fP option. (Added in
7.10.6)
.RS
.IP CURLAUTH_BASIC
HTTP Basic authentication. This is the default choice, and the only method
that is in wide-spread use and supported virtually everywhere. This is sending
the user name and password over the network in plain text, easily captured by
others.
.IP CURLAUTH_DIGEST
HTTP Digest authentication.  Digest authentication is defined in RFC2617 and
is a more secure way to do authentication over public networks than the
regular old-fashioned Basic method.
.IP CURLAUTH_GSSNEGOTIATE
HTTP GSS-Negotiate authentication. The GSS-Negotiate (also known as plain
\&"Negotiate") method was designed by Microsoft and is used in their web
applications. It is primarily meant as a support for Kerberos5 authentication
but may be also used along with another authentication methods. For more
information see IETF draft draft-brezak-spnego-http-04.txt.

You need to build libcurl with a suitable GSS-API library for this to work.
.IP CURLAUTH_NTLM
HTTP NTLM authentication. A proprietary protocol invented and used by
Microsoft. It uses a challenge-response and hash concept similar to Digest, to
prevent the password from being eavesdropped.

You need to build libcurl with OpenSSL support for this option to work, or
build libcurl on Windows.
.IP CURLAUTH_ANY
This is a convenience macro that sets all bits and thus makes libcurl pick any
it finds suitable. libcurl will automatically select the one it finds most
secure.
.IP CURLAUTH_ANYSAFE
This is a convenience macro that sets all bits except Basic and thus makes
libcurl pick any it finds suitable. libcurl will automatically select the one it
finds most secure.
.RE
.IP CURLOPT_PROXYAUTH
Pass a long as parameter, which is set to a bitmask, to tell libcurl what
authentication method(s) you want it to use for your proxy authentication.  If
more than one bit is set, libcurl will first query the site to see what
authentication methods it supports and then pick the best one you allow it to
use. For some methods, this will induce an extra network round-trip. Set the
actual name and password with the \fICURLOPT_PROXYUSERPWD\fP option. The
bitmask can be constructed by or'ing together the bits listed above for the
\fICURLOPT_HTTPAUTH\fP option. As of this writing, only Basic, Digest and NTLM
work. (Added in 7.10.7)
.SH HTTP OPTIONS
.IP CURLOPT_AUTOREFERER
Pass a non-zero parameter to enable this. When enabled, libcurl will
automatically set the Referer: field in requests where it follows a Location:
redirect.
.IP CURLOPT_ENCODING
Sets the contents of the Accept-Encoding: header sent in an HTTP
request, and enables decoding of a response when a Content-Encoding:
header is received.  Three encodings are supported: \fIidentity\fP,
which does nothing, \fIdeflate\fP which requests the server to
compress its response using the zlib algorithm, and \fIgzip\fP which
requests the gzip algorithm.  If a zero-length string is set, then an
Accept-Encoding: header containing all supported encodings is sent.

This is a request, not an order; the server may or may not do it.  This
option must be set (to any non-NULL value) or else any unsolicited
encoding done by the server is ignored. See the special file
lib/README.encoding for details.
.IP CURLOPT_FOLLOWLOCATION
A non-zero parameter tells the library to follow any Location: header that the
server sends as part of an HTTP header.

This means that the library will re-send the same request on the new location
and follow new Location: headers all the way until no more such headers are
returned. \fICURLOPT_MAXREDIRS\fP can be used to limit the number of redirects
libcurl will follow.
.IP CURLOPT_UNRESTRICTED_AUTH
A non-zero parameter tells the library it can continue to send authentication
(user+password) when following locations, even when hostname changed. This
option is meaningful only when setting \fICURLOPT_FOLLOWLOCATION\fP.
.IP CURLOPT_MAXREDIRS
Pass a long. The set number will be the redirection limit. If that many
redirections have been followed, the next redirect will cause an error
(\fICURLE_TOO_MANY_REDIRECTS\fP). This option only makes sense if the
\fICURLOPT_FOLLOWLOCATION\fP is used at the same time. Added in 7.15.1:
Setting the limit to 0 will make libcurl refuse any redirect. Set it to -1 for
an infinite number of redirects (which is the default)
.IP CURLOPT_POST301
A non-zero parameter tells the library to respect RFC 2616/10.3.2 and not
convert POST requests into GET requests when following a 301 redirection. The
non-RFC behaviour is ubiquitous in web browsers, so the library does the
conversion by default to maintain consistency. However, a server may requires
a POST to remain a POST after such a redirection. This option is meaningful
only when setting \fICURLOPT_FOLLOWLOCATION\fP.  (Added in 7.17.1)
.IP CURLOPT_PUT
A non-zero parameter tells the library to use HTTP PUT to transfer data. The
data should be set with \fICURLOPT_READDATA\fP and \fICURLOPT_INFILESIZE\fP.

This option is deprecated and starting with version 7.12.1 you should instead
use \fICURLOPT_UPLOAD\fP.
.IP CURLOPT_POST
A non-zero parameter tells the library to do a regular HTTP post. This will
also make the library use the a "Content-Type:
application/x-www-form-urlencoded" header. (This is by far the most commonly
used POST method).

Use one of \fICURLOPT_POSTFIELDS\fP or \fICURLOPT_COPYPOSTFIELDS\fP options to
specify what data to post and \fICURLOPT_POSTFIELDSIZE\fP or
\fICURLOPT_POSTFIELDSIZE_LARGE\fP to set the data size.

Optionally, you can provide data to POST using the \fICURLOPT_READFUNCTION\fP
and \fICURLOPT_READDATA\fP options but then you must make sure to not set
\fICURLOPT_POSTFIELDS\fP to anything but NULL. When providing data with a
callback, you must transmit it using chunked transfer-encoding or you must set
the size of the data with the \fICURLOPT_POSTFIELDSIZE\fP or
\fICURLOPT_POSTFIELDSIZE_LARGE\fP option.

You can override the default POST Content-Type: header by setting your own
with \fICURLOPT_HTTPHEADER\fP.

Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header.
You can disable this header with \fICURLOPT_HTTPHEADER\fP as usual.

If you use POST to a HTTP 1.1 server, you can send data without knowing the
size before starting the POST if you use chunked encoding. You enable this by
adding a header like "Transfer-Encoding: chunked" with
\fICURLOPT_HTTPHEADER\fP. With HTTP 1.0 or without chunked transfer, you must
specify the size in the request.

When setting \fICURLOPT_POST\fP to a non-zero value, it will automatically set
\fICURLOPT_NOBODY\fP to 0 (since 7.14.1).

If you issue a POST request and then want to make a HEAD or GET using the same
re-used handle, you must explicitly set the new request type using
\fICURLOPT_NOBODY\fP or \fICURLOPT_HTTPGET\fP or similar.
.IP CURLOPT_POSTFIELDS
Pass a void * as parameter, which should be the full data to post in an HTTP
POST operation. You must make sure that the data is formatted the way you want
the server to receive it. libcurl will not convert or encode it for you. Most
web servers will assume this data to be url-encoded. Take note.

The pointed data are NOT copied by the library: as a consequence, they must
be preserved by the calling application until the transfer finishes.

This POST is a normal application/x-www-form-urlencoded kind (and libcurl will
set that Content-Type by default when this option is used), which is the most
commonly used one by HTML forms. See also the \fICURLOPT_POST\fP. Using
\fICURLOPT_POSTFIELDS\fP implies \fICURLOPT_POST\fP.

If you want to do a zero-byte POST, you need to set
\fICURLOPT_POSTFIELDSIZE\fP explicitly to zero, as simply setting
\fICURLOPT_POSTFIELDS\fP to NULL or "" just effectively disables the sending
of the specified string. libcurl will instead assume that you'll send the POST
data using the read callback!

Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header.
You can disable this header with \fICURLOPT_HTTPHEADER\fP as usual.

To make multipart/formdata posts (aka rfc1867-posts), check out the
\fICURLOPT_HTTPPOST\fP option.
.IP CURLOPT_POSTFIELDSIZE
If you want to post data to the server without letting libcurl do a strlen()
to measure the data size, this option must be used. When this option is used
you can post fully binary data, which otherwise is likely to fail. If this
size is set to -1, the library will use strlen() to get the size.
.IP CURLOPT_POSTFIELDSIZE_LARGE
Pass a curl_off_t as parameter. Use this to set the size of the
\fICURLOPT_POSTFIELDS\fP data to prevent libcurl from doing strlen() on the
data to figure out the size. This is the large file version of the
\fICURLOPT_POSTFIELDSIZE\fP option. (Added in 7.11.1)
.IP CURLOPT_COPYPOSTFIELDS
Pass a char * as parameter, which should be the full data to post in an HTTP
POST operation. It behaves as the \fICURLOPT_POSTFIELDS\fP option, but the
original data are copied by the library, allowing the application to overwrite
the original data after setting this option.

Because data are copied, care must be taken when using this option in
conjunction with \fICURLOPT_POSTFIELDSIZE\fP or
\fICURLOPT_POSTFIELDSIZE_LARGE\fP: If the size has not been set prior to
\fICURLOPT_COPYPOSTFIELDS\fP, the data are assumed to be a NUL-terminated
string; else the stored size informs the library about the data byte count to
copy. In any case, the size must not be changed after
\fICURLOPT_COPYPOSTFIELDS\fP, unless another \fICURLOPT_POSTFIELDS\fP or
\fICURLOPT_COPYPOSTFIELDS\fP option is issued.
(Added in 7.17.1)

.IP CURLOPT_HTTPPOST
Tells libcurl you want a multipart/formdata HTTP POST to be made and you
instruct what data to pass on to the server.  Pass a pointer to a linked list
of curl_httppost structs as parameter. . The easiest way to create such a