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curl_multi_wait(3)              libcurl Manual              curl_multi_wait(3)




NAME

       curl_multi_wait - polls on all easy handles in a multi handle


SYNOPSIS

       #include <curl/curl.h>

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


DESCRIPTION

       curl_multi_wait(3)  polls  all  file  descriptors used by the curl easy
       handles contained in the given multi handle set.  It will  block  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 will be 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 will be 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.

       If no extra file descriptors are  provided  and  libcurl  has  no  file
       descriptor to offer to wait for, this function will return immediately.

       This function is encouraged to be used instead of select(3) when  using
       the multi interface to allow applications to easier circumvent the com-
       mon 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.


EXAMPLE

       CURL *easy_handle;
       CURLM *multi_handle;

       /* 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 ) {
           /* wait for activity, timeout or "nothing" */
           mc = curl_multi_wait(multi_handle, NULL, 0, 1000, &numfds);
         }

         if(mc != CURLM_OK) {
           fprintf(stderr, "curl_multi failed, code %d.0, mc);
           break;
         }

         /* 'numfds' being zero means either a timeout or no file descriptors to
            wait for. Try timeout on first occurrence, then assume no file
            descriptors and no file descriptors to wait for means wait for 100
            milliseconds. */

         if(!numfds) {
           repeats++; /* count number of repeated zero numfds */
           if(repeats > 1) {
             WAITMS(100); /* sleep 100 milliseconds */
           }
         }
         else
           repeats = 0;

       } while(still_running);

       curl_multi_remove_handle(multi_handle, easy_handle);


RETURN VALUE

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


AVAILABILITY

       This function was added in libcurl 7.28.0.


SEE ALSO

       curl_multi_fdset(3), curl_multi_perform(3)



libcurl 7.28.0                    12 Jul 2012               curl_multi_wait(3)

curl 7.48.0 - Generated Tue Mar 29 18:33:27 CDT 2016
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