event_add() schedules the execution of the event
when the event specified in event_set() occurs or in at least the time
specified by the timeout argument. If
timeout was not specified, not timeout is set. The
event must be already initalized by event_set()
and event_base_set() functions. If the
event already has a timeout set, it is replaced by
the new one.
인수
event
Valid event resource.
timeout
Optional timeout (in microseconds).
반환값
event_add() returns TRUE on success or FALSE on error.