curl_multi_timeout(3)

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_ms 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 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 = 2;
  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).

SEE ALSO
curl_multi_fdset(3), curl_multi_info_read(3), curl_multi_setopt(3), curl_multi_socket(3)