curl/docs/libcurl/curl_multi_setopt.3

.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
.\" * are also available at http://curl.haxx.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" **************************************************************************
.TH curl_multi_setopt 3 "10 Oct 2006" "libcurl 7.16.0" "libcurl Manual"
.SH NAME
curl_multi_setopt \- set options for a curl multi handle
.SH SYNOPSIS
#include <curl/curl.h>

CURLMcode curl_multi_setopt(CURLM * multi_handle, CURLMoption option, param);
.SH DESCRIPTION
curl_multi_setopt() is used to tell a libcurl multi handle how to behave. By
using the appropriate options to \fIcurl_multi_setopt(3)\fP, you can change
libcurl's behaviour when using that multi handle.  All options are set with
the \fIoption\fP followed by the parameter \fIparam\fP. That parameter can be
a \fBlong\fP, a \fBfunction pointer\fP, an \fBobject pointer\fP or a
\fBcurl_off_t\fP type, depending on what the specific option expects. Read
this manual carefully as bad input values may cause libcurl to behave badly!
You can only set one option in each function call.

.SH OPTIONS
.IP CURLMOPT_SOCKETFUNCTION
Pass a pointer to a function matching the \fBcurl_socket_callback\fP
prototype. The \fIcurl_multi_socket_action(3)\fP function informs the
application about updates in the socket (file descriptor) status by doing
none, one, or multiple calls to the curl_socket_callback given in the
\fBparam\fP argument. They update the status with changes since the previous
time a \fIcurl_multi_socket(3)\fP function was called. If the given callback
pointer is NULL, no callback will be called. Set the callback's \fBuserp\fP
argument with \fICURLMOPT_SOCKETDATA\fP.  See \fIcurl_multi_socket(3)\fP for
more callback details.
.IP CURLMOPT_SOCKETDATA
Pass a pointer to whatever you want passed to the \fBcurl_socket_callback\fP's
fourth argument, the userp pointer. This is not used by libcurl but only
passed-thru as-is. Set the callback pointer with
\fICURLMOPT_SOCKETFUNCTION\fP.
.IP CURLMOPT_PIPELINING
Pass a long set to 1 to enable or 0 to disable. Enabling pipelining on a multi
handle will make it attempt to perform HTTP Pipelining as far as possible for
transfers using this handle. This means that if you add a second request that
can use an already existing connection, the second request will be \&"piped"
on the same connection rather than being executed in parallel. (Added in
7.16.0)
.IP CURLMOPT_TIMERFUNCTION
Pass a pointer to a function matching the \fBcurl_multi_timer_callback\fP
prototype: int curl_multi_timer_callback(CURLM *multi /* multi handle */,
long timeout_ms /* timeout in milliseconds */, void *userp /* TIMERDATA */).
This function will then be called when the timeout value
changes. The timeout value is at what latest time the application should call
one of the \&"performing" functions of the multi interface
(\fIcurl_multi_socket_action(3)\fP and \fIcurl_multi_perform(3)\fP) - to allow
libcurl to keep timeouts and retries etc to work. A timeout value of -1 means
that there is no timeout at all, and 0 means that the timeout is already
reached. Libcurl attempts to limit calling this only when the fixed future
timeout time actually changes. See also \fICURLMOPT_TIMERDATA\fP. The callback
should return 0 on success, and -1 on error. This
callback can be used instead of, or in addition to,
\fIcurl_multi_timeout(3)\fP. (Added in 7.16.0)
.IP CURLMOPT_TIMERDATA
Pass a pointer to whatever you want passed to the
\fBcurl_multi_timer_callback\fP's third argument, the userp pointer.  This is
not used by libcurl but only passed-thru as-is. Set the callback pointer with
\fICURLMOPT_TIMERFUNCTION\fP. (Added in 7.16.0)
.IP CURLMOPT_MAXCONNECTS
Pass a long. The set number will be used as the maximum amount of
simultaneously open connections that libcurl may cache. Default is 10, and
libcurl will enlarge the size for each added easy handle to make it fit 4
times the number of added easy handles.

By setting this option, you can prevent the cache size from growing beyond the
limit set by you.

When the cache is full, curl closes the oldest one in the cache to prevent the
number of open connections from increasing.

This option is for the multi handle's use only, when using the easy interface
you should instead use the \fICURLOPT_MAXCONNECTS\fP option.

(Added in 7.16.3)
.IP CURLMOPT_MAX_HOST_CONNECTIONS
Pass a long. The set number will be used as the maximum amount of
simultaneously open connections to a single host. For each new session to
a host, libcurl will open a new connection up to the limit set by
CURLMOPT_MAX_HOST_CONNECTIONS. When the limit is reached, the sessions will
be pending until there are available connections. If CURLMOPT_PIPELINING is
1, libcurl will try to pipeline if the host is capable of it.

The default value is 0, which means that there is no limit.
However, for backwards compatibility, setting it to 0 when CURLMOPT_PIPELINING
is 1 will not be treated as unlimited. Instead it will open only 1 connection
and try to pipeline on it.

(Added in 7.30.0)
.IP CURLMOPT_MAX_PIPELINE_LENGTH
Pass a long. The set number will be used as the maximum amount of requests
in a pipelined connection. When this limit is reached, libcurl will use another
connection to the same host (see CURLMOPT_MAX_HOST_CONNECTIONS), or queue the
requests until one of the pipelines to the host is ready to accept a request.
Thus, the total number of requests in-flight is CURLMOPT_MAX_HOST_CONNECTIONS *
CURLMOPT_MAX_PIPELINE_LENGTH.
The default value is 5.

(Added in 7.30.0)
.IP CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE
Pass a long. If a pipelined connection is currently processing a request
with a Content-Length larger than CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE, that
connection will not be considered for additional requests, even if it is
shorter than CURLMOPT_MAX_PIPELINE_LENGTH.
The default value is 0, which means that the penalization is inactive.

(Added in 7.30.0)
.IP CURLMOPT_CHUNK_LENGTH_PENALTY_SIZE
Pass a long. If a pipelined connection is currently processing a
chunked (Transfer-encoding: chunked) request with a current chunk length
larger than CURLMOPT_CHUNK_LENGTH_PENALTY_SIZE, that connection will not be
considered for additional requests, even if it is shorter than
CURLMOPT_MAX_PIPELINE_LENGTH.
The default value is 0, which means that the penalization is inactive.

(Added in 7.30.0)
.IP CURLMOPT_PIPELINING_SITE_BL
Pass an array of char *, ending with NULL. This is a list of sites that are
blacklisted from pipelining, i.e sites that are known to not support HTTP
pipelining. The array is copied by libcurl.

The default value is NULL, which means that there is no blacklist.

Pass a NULL pointer to clear the blacklist.

Example:

.nf
  site_blacklist[] =
  {
    "www.haxx.se",
    "www.example.com:1234",
    NULL
  };

  curl_multi_setopt(m, CURLMOPT_PIPELINE_SITE_BL, site_blacklist);
.fi

(Added in 7.30.0)
.IP CURLMOPT_PIPELINING_SERVER_BL
Pass an array of char *, ending with NULL. This is a list of server types
prefixes (in the Server: HTTP header) that are blacklisted from pipelining,
i.e server types that are known to not support HTTP pipelining. The array is
copied by libcurl.

Note that the comparison matches if the Server: header begins with the string
in the blacklist, i.e "Server: Ninja 1.2.3" and "Server: Ninja 1.4.0" can 
both be blacklisted by having "Ninja" in the backlist.

The default value is NULL, which means that there is no blacklist.

Pass a NULL pointer to clear the blacklist.

Example:

.nf
  server_blacklist[] =
  {
    "Microsoft-IIS/6.0",
    "nginx/0.8.54",
    NULL
  };

  curl_multi_setopt(m, CURLMOPT_PIPELINE_SERVER_BL, server_blacklist);
.fi

(Added in 7.30.0)
.IP CURLMOPT_MAX_TOTAL_CONNECTIONS
Pass a long. The set number will be used as the maximum amount of
simultaneously open connections in total. For each new session, libcurl
will open a new connection up to the limit set by
CURLMOPT_MAX_TOTAL_CONNECTIONS. When the limit is reached, the sessions will
be pending until there are available connections. If CURLMOPT_PIPELINING is
1, libcurl will try to pipeline if the host is capable of it.

The default value is 0, which means that there is no limit.
However, for backwards compatibility, setting it to 0 when CURLMOPT_PIPELINING
is 1 will not be treated as unlimited. Instead it will open only 1 connection
and try to pipeline on it.

(Added in 7.30.0)
.SH RETURNS
The standard CURLMcode for multi interface error codes. Note that it returns a
CURLM_UNKNOWN_OPTION if you try setting an option that this version of libcurl
doesn't know of.
.SH AVAILABILITY
This function was added in libcurl 7.15.4.
.SH "SEE ALSO"
.BR curl_multi_cleanup "(3), " curl_multi_init "(3), "
.BR curl_multi_socket "(3), " curl_multi_info_read "(3)"