curl_multi_perform man page on Archlinux

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curl_multi_perform(3)		libcurl Manual		 curl_multi_perform(3)

       curl_multi_perform - reads/writes available data from each easy handle

       #include <curl/curl.h>

       CURLMcode  curl_multi_perform(CURLM  *multi_handle,  int	 *running_han‐

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

       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 han‐
       dle), 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.

       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 "satis‐
       fied".	 Do    note    that    curl_multi_perform(3)	will	return
       CURLM_CALL_MULTI_PERFORM	 only when it wants to be called again immedi‐
       ately. 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.

       Most  applications  will	 use curl_multi_fdset(3) to get the multi_han‐
       dle'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.

       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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