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curl_multi_perform(3)           libcurl Manual           curl_multi_perform(3)



NAME
       curl_multi_perform - reads/writes available data from each easy handle

SYNOPSIS
       #include <curl/curl.h>

       CURLMcode curl_multi_perform(CURLM *multi_handle, int *running_handles);

DESCRIPTION
       When  the  app  thinks  there's data available for the multi_handle, it should call this function to read/write
       whatever there is to read or write right now. curl_multi_perform() returns as  soon  as  the  reads/writes  are
       done.  This function does not require that there actually is any data available for reading or that data can be
       written, it can be called just in case. It will write the number of handles that still  transfer  data  in  the
       second argument's integer-pointer.

       When  you  call curl_multi_perform() and the amount of running_handles is changed from the previous call (or is
       less than the amount of easy handles you've added to the multi handle), you know that  there  is  one  or  more
       transfers  less  "running".  You can then call curl_multi_info_read(3) to get information about each individual
       completed transfer, and that returned info includes CURLcode and more. If an added handle fails  very  quickly,
       it may never be counted as a running_handle.

       When  running_handles  is  set  to zero (0) on the return of this function, there is no longer any transfers in
       progress.

RETURN VALUE
       CURLMcode type, general libcurl multi interface error code.

       Before version 7.20.0: If you receive CURLM_CALL_MULTI_PERFORM, this  basically  means  that  you  should  call
       curl_multi_perform  again,  before  you  select() on more actions. You don't have to do it immediately, but the
       return code means that libcurl may have more data available to return or that there may be more  data  to  send
       off before it is "satisfied". Do note that curl_multi_perform(3) will return CURLM_CALL_MULTI_PERFORM only when
       it wants to be called again immediately. When things are fine and there is nothing  immediate  it  wants  done,
       it'll return CURLM_OK and you need to wait for "action" and then call this function again.

       This  function  only returns errors etc regarding the whole multi stack.  Problems still might have occurred on
       individual transfers even when this function returns CURLM_OK.

TYPICAL USAGE
       Most applications will use curl_multi_fdset(3) to get the multi_handle's file descriptors, then it'll wait  for
       action on them using select(3) and as soon as one or more of them are ready, curl_multi_perform(3) gets called.

SEE ALSO
       curl_multi_cleanup(3), curl_multi_init(3), curl_multi_fdset(3), curl_multi_info_read(3), libcurl-errors(3)



libcurl 7.9.5                    1 March 2002            curl_multi_perform(3)