curl_multi_fdset(3) [osx man page]

curl_multi_fdset(3)						  libcurl Manual					       curl_multi_fdset(3)

NAME

       curl_multi_fdset - extracts file descriptor information from a multi handle

SYNOPSIS

       #include <curl/curl.h>

       CURLMcode curl_multi_fdset(CURLM *multi_handle,
				  fd_set *read_fd_set,
				  fd_set *write_fd_set,
				  fd_set *exc_fd_set,
				  int *max_fd);

DESCRIPTION

       This  function  extracts  file  descriptor information from a given multi_handle.  libcurl returns its fd_set sets. The application can use
       these to select() on, but be sure to FD_ZERO them before calling this function as curl_multi_fdset(3) only adds	its  own  descriptors,	it
       doesn't zero or otherwise remove any others. The curl_multi_perform(3) function should be called as soon as one of them is ready to be read
       from or written to.

       If no file descriptors are set by libcurl, max_fd will contain -1 when this function returns. Otherwise it will contain the higher descrip-
       tor  number  libcurl  set.  When  libcurl returns -1 in max_fd, it is because libcurl currently does something that isn't possible for your
       application to monitor with a socket and unfortunately you can then not know exactly when the current action is completed  using  select().
       When  max_fd  returns with -1, you need to wait a while and then proceed and call curl_multi_perform anyway. How long to wait? I would sug-
       gest 100 milliseconds at least, but you may want to test it out in your own particular conditions to find a suitable value.

       When doing select(), you should use curl_multi_timeout to figure out how long to wait for action. Call curl_multi_perform even if no activ-
       ity has been seen on the fd_sets after the timeout expires as otherwise internal retries and timeouts may not work as you'd think and want.

       If  one	of  the sockets used by libcurl happens to be larger than what can be set in an fd_set, which on POSIX systems means that the file
       descriptor is larger than FD_SETSIZE, then libcurl will try to not set it. Setting a too large file descriptor in an fd_set implies an  out
       of  bounds  write which can cause crashes, or worse. The effect of NOT storing it will possibly save you from the crash, but will make your
       program NOT wait for sockets it should wait for...

RETURN VALUE

       CURLMcode type, general libcurl multi interface error code. See libcurl-errors(3)

SEE ALSO

       curl_multi_cleanup(3), curl_multi_init(3), curl_multi_timeout(3), curl_multi_perform(3)

libcurl 7.16.0							    2 Jan 2006						       curl_multi_fdset(3)

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 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
       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.	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.

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 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.

       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.

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)