NAME

       curl_multi_poll - poll on all easy handles in a multi handle

SYNOPSIS

       #include <curl/curl.h>

       CURLMcode curl_multi_poll(CURLM *multi_handle,
                                 struct curl_waitfd extra_fds[],
                                 unsigned int extra_nfds,
                                 int timeout_ms,
                                 int *numfds);

DESCRIPTION

       curl_multi_poll(3)  polls  all file descriptors used by the curl easy handles contained in
       the given multi handle set. It blocks until activity is detected on at least  one  of  the
       handles  or  timeout_ms  has  passed.   Alternatively,  if  the multi handle has a pending
       internal timeout that has a shorter expiry time than timeout_ms, that shorter time is used
       instead to make sure timeout accuracy is reasonably kept.

       The  calling  application  may pass additional curl_waitfd structures which are similar to
       poll(2)'s pollfd structure to be waited on in the same call.

       On completion, if numfds is non-NULL, it gets populated with  the  total  number  of  file
       descriptors  on  which  interesting  events occurred. This number can include both libcurl
       internal descriptors as well as descriptors provided in extra_fds.

       The curl_multi_wakeup(3) function can be used from another thread to wake up this function
       and  return  faster.  This  is  one of the details that makes this function different than
       curl_multi_wait(3) which cannot be woken up this way.

       If no extra file descriptors are provided and libcurl has no file descriptor to  offer  to
       wait  for,  this  function  instead waits during timeout_ms milliseconds (or shorter if an
       internal timer indicates so). This is the other detail that makes this function  different
       than curl_multi_wait(3).

       This function is encouraged to be used instead of select(3) when using the multi interface
       to allow applications to easier circumvent the  common  problem  with  1024  maximum  file
       descriptors.

curl_waitfd

       struct curl_waitfd {
         curl_socket_t fd;
         short events;
         short revents;
       };

       CURL_WAIT_POLLIN
              Bit  flag  to  curl_waitfd.events  indicating the socket should poll on read events
              such as new data received.

       CURL_WAIT_POLLPRI
              Bit flag to curl_waitfd.events indicating the socket should poll on  high  priority
              read events such as out of band data.

       CURL_WAIT_POLLOUT
              Bit  flag  to  curl_waitfd.events indicating the socket should poll on write events
              such as the socket being clear to write without blocking.

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       extern void handle_fd(int);

       int main(void)
       {
         CURL *easy_handle;
         CURLM *multi_handle;
         int still_running = 0;
         int myfd; /* this is our own file descriptor */

         /* add the individual easy handle */
         curl_multi_add_handle(multi_handle, easy_handle);

         do {
           CURLMcode mc;
           int numfds;

           mc = curl_multi_perform(multi_handle, &still_running);

           if(mc == CURLM_OK) {
             struct curl_waitfd myown;
             myown.fd = myfd;
             myown.events = CURL_WAIT_POLLIN; /* wait for input */
             myown.revents = 0; /* clear it */

             /* wait for activity on curl's descriptors or on our own,
                or timeout */
             mc = curl_multi_poll(multi_handle, &myown, 1, 1000, &numfds);

             if(myown.revents) {
               /* did our descriptor receive an event? */
               handle_fd(myfd);
             }
           }

           if(mc != CURLM_OK) {
             fprintf(stderr, "curl_multi failed, code %d.\n", mc);
             break;
           }

         } while(still_running);

         curl_multi_remove_handle(multi_handle, easy_handle);
       }

AVAILABILITY

       Added in curl 7.66.0

RETURN VALUE

       CURLMcode type, general libcurl multi interface error code. See libcurl-errors(3)

SEE ALSO

       curl_multi_fdset(3), curl_multi_perform(3), curl_multi_wait(3), curl_multi_wakeup(3)