Tribblix: manual page: curl_multi

curl_multi_timeout(3) Introduction to Library Functions

NAME

curl_multi_timeout - how long to wait for action before proceeding

SYNOPSIS

#include <curl/curl.h>

CURLMcode curl_multi_timeout(CURLM *multi_handle, long *timeout);

DESCRIPTION

An application using the libcurl multi interface should call
curl_multi_timeout(3) to figure out how long it should wait for
socket actions - at most - before proceeding.

Proceeding means either doing the socket-style timeout action: call
the curl_multi_socket_action(3) function with the sockfd argument set
to CURL_SOCKET_TIMEOUT, or call curl_multi_perform(3) if you are
using the simpler and older multi interface approach.

The timeout value returned in the long timeout points to, is in
number of milliseconds at this moment. If 0, it means you should
proceed immediately without waiting for anything. If it returns -1,
there is no timeout at all set.

An application that uses the multi_socket API should not use this
function. It should instead use the CURLMOPT_TIMERFUNCTION(3) option
for proper and desired behavior.

Note: if libcurl returns a -1 timeout here, it just means that
libcurl currently has no stored timeout value. You must not wait too
long (more than a few seconds perhaps) before you call
curl_multi_perform(3) again.

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
struct timeval timeout;
long timeo;
fd_set fdread;
fd_set fdwrite;
fd_set fdexcep;
int maxfd;
CURLM *multi = curl_multi_init();

curl_multi_timeout(multi, &timeo);
if(timeo < 0)
/* no set timeout, use a default */
timeo = 980;

timeout.tv_sec = timeo / 1000;
timeout.tv_usec = (timeo % 1000) * 1000;

/* wait for activities no longer than the set timeout */
select(maxfd + 1, &fdread, &fdwrite, &fdexcep, &timeout);
}

TYPICAL USAGE

Call curl_multi_timeout(3), then wait for action on the sockets.
Figure out which sockets to wait for by calling curl_multi_fdset(3).

When there is activity or timeout, call curl_multi_perform(3) and
then loop - until all transfers are complete.

AVAILABILITY

Added in curl 7.15.4

RETURN VALUE

This function returns a CURLMcode indicating success or error.

CURLM_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).