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SIGEVENT(7)		   Linux Programmer's Manual		   SIGEVENT(7)

       sigevent - structure for notification from asynchronous routines

       union sigval {	       /* Data passed with notification */
	   int	   sival_int;	      /* Integer value */
	   void	  *sival_ptr;	      /* Pointer value */

       struct sigevent {
	   int		sigev_notify; /* Notification method */
	   int		sigev_signo;  /* Notification signal */
	   union sigval sigev_value;  /* Data passed with
					 notification */
	   void	      (*sigev_notify_function) (union sigval);
			    /* Function used for thread
			       notification (SIGEV_THREAD) */
	   void	       *sigev_notify_attributes;
			    /* Attributes for notification thread
			       (SIGEV_THREAD) */
	   pid_t	sigev_notify_thread_id;
			    /* ID of thread to signal (SIGEV_THREAD_ID) */

       The  sigevent  structure	 is used by various APIs to describe the way a
       process is to be notified about an event (e.g., completion of an	 asyn-
       chronous request, expiration of a timer, or the arrival of a message).

       The definition shown in the SYNOPSIS is approximate: some of the fields
       in the sigevent structure may be defined as part of a union.   Programs
       should  employ  only  those  fields  relevant to the value specified in

       The sigev_notify field specifies how notification is to	be  performed.
       This field can have one of the following values:

	       A "null" notification: don't do anything when the event occurs.

	       Notify	the   process  by  sending  the	 signal	 specified  in

	       If the signal is caught with a signal handler that  was	regis-
	       tered  using the sigaction(2) SA_SIGINFO flag, then the follow-
	       ing fields are set in the siginfo_t structure that is passed as
	       the second argument of the handler:

	       si_code	 This  field is set to a value that depends on the API
			 delivering the notification.

	       si_signo	 This field is set to the  signal  number  (i.e.,  the
			 same value as in sigev_signo).

	       si_value	 This	field	is  set	 to  the  value	 specified  in

	       Depending on the API, other fields may also be set in the  sig-
	       info_t structure.

	       The  same  information  is  also	 available  if	the  signal is
	       accepted using sigwaitinfo(2).

	       Notify the process by invoking sigev_notify_function "as if" it
	       were  the start function of a new thread.  (Among the implemen-
	       tation possibilities here  are  that  each  timer  notification
	       could  result in the creation of a new thread, or that a single
	       thread is created to receive all notifications.)	 The  function
	       is   invoked   with  sigev_value	 as  its  sole	argument.   If
	       sigev_notify_attributes is not  NULL,  it  should  point	 to  a
	       pthread_attr_t  structure  that	defines attributes for the new
	       thread (see pthread_attr_init(3)).

       SIGEV_THREAD_ID (Linux-specific)
	       Currently used only by POSIX timers; see timer_create(2).

       timer_create(2),	 aio_fsync(3),	 aio_read(3),	aio_write(3),	getad-
       drinfo_a(3), lio_listio(3), mq_notify(3), aio(7), pthreads(7)

       This  page  is  part of release 4.10 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at

GNU				  2015-08-08			   SIGEVENT(7)