curl_multi_perform(3)     libcurl Manual    curl_multi_perform(3)



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

SYNOPSIS
       #include 

       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 actu-
       ally 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 run-
       ning_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.

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

       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  are
       nothing immediate it wants done, it'll return CURLM_OK and
       you need to wait for "action" and then call this  function
       again.

       NOTE that this only returns errors etc regarding the whole
       multi stack. There might still have occurred  problems  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)