sigevent(7) — Linux manual page


sigevent(7)         Miscellaneous Information Manual         sigevent(7)

NAME         top

       sigevent - structure for notification from asynchronous routines

SYNOPSIS         top

       #include <signal.h>

       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); Linux-specific */

DESCRIPTION         top

       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 asynchronous 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 sigev_notify.

       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

              Notify the process by sending the signal specified in

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

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

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

                     This field is set to the value specified in

              Depending on the API, other fields may also be set in the
              siginfo_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 implementation 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

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

SEE ALSO         top

       timer_create(2), aio_fsync(3), aio_read(3), aio_write(3),
       getaddrinfo_a(3), lio_listio(3), mq_notify(3), aio(7),

Linux man-pages (unreleased)     (date)                      sigevent(7)

Pages that refer to this page: timer_create(2)aio_cancel(3)aio_fsync(3)aio_read(3)aio_write(3)getaddrinfo_a(3)lio_listio(3)mq_notify(3)aio(7)pthreads(7)signal(7)system_data_types(7)