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 youre 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 very moment. If 0, it means you should proceed
immediately without waiting for anything. If it returns -1, theres no timeout
at all set.
An application that uses the multi_socket API SHOULD NOT use this function, but
SHOULD instead use curl_multi_setopt(3) and its
CURLMOPT_TIMERFUNCTION 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() again.
struct timeval timeout;
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);