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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  han-dles handles
       dles 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.

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 is nothing immedi-ate immediate
       ate it wants done, it'll return CURLM_OK and you need to wait for "action" and then call  this  func-tion function
       tion again.

       NOTE  that  this  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_per-form(3) curl_multi_perform(3)
       form(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) libcurlerrors(3)
       errors(3)



libcurl 7.9.5                                   1 March 2002                           curl_multi_perform(3)