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

       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)

libcurl                                            2024-12-11                                 curl_multi_poll(3)