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_han‐
       dles);

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 running_handles is
       changed from the previous call (or is less than the amount of easy han‐
       dles 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 transfer, and that returned info includes CURLcode and more.

       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.

       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.

       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_han‐
       dle'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) 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)

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