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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
       This function handles transfers on all the added handles that need attention in an non-blocking fash-ion. fashion.
       ion.

       When an application has found out there's data available  for  the  multi_handle  or  a  timeout  has
       elapsed,  the  application should call this function to read/write whatever there is to read or write
       right now etc.  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.

       If  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 com-pleted completed
       pleted 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 trans-fers transfers
       fers 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 immedi-ately, immediately,
       ately, 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.   Use
       curl_multi_info_read(3) to figure out how individual transfers did.

TYPICAL USAGE
       Most applications will use curl_multi_fdset(3)  to  get  the  multi_handle's  file  descriptors,  and
       curl_multi_timeout(3)  to  get  a  suitable  timeout  period,  then it'll wait for action on the file
       descriptors using select(3). As soon as one or more file descriptor is  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) libcurlerrors(3)
       errors(3)



libcurl 7.9.5                                   1 March 2002                           curl_multi_perform(3)