sigevent(3type) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON

sigevent(3type)                                          sigevent(3type)

NAME         top

       sigevent, sigval - structure for notification from asynchronous
       routines

SYNOPSIS         top

       #include <signal.h>

       struct sigevent {
           int             sigev_notify;  /* Notification type */
           int             sigev_signo;   /* Signal number */
           union sigval    sigev_value;   /* Data passed with notification */

           void          (*sigev_notify_function)(union sigval);
                                          /* Notification function
                                             (SIGEV_THREAD) */
           pthread_attr_t *sigev_notify_attributes;
                                          /* Notification attributes */

           /* Linux only: */
           pid_t           sigev_notify_thread_id;
                                          /* ID of thread to signal
                                             (SIGEV_THREAD_ID) */
       };

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

DESCRIPTION         top

   sigevent
       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:

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

       SIGEV_SIGNAL
              Notify the process by sending the signal specified in
              sigev_signo.

              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:

              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
                     sigev_value.

              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).

       SIGEV_THREAD
              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
              pthread_attr_init(3)).

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

   sigval
       Data passed with a signal.

STANDARDS         top

       POSIX.1-2008.

HISTORY         top

       POSIX.1-2001.

       <aio.h> and <time.h> define sigevent since POSIX.1-2008.

NOTES         top

       The following headers also provide sigevent: <aio.h>, <mqueue.h>,
       and <time.h>.

SEE ALSO         top

       timer_create(2), getaddrinfo_a(3), lio_listio(3), mq_notify(3),
       pthread_sigqueue(3), sigqueue(3), aiocb(3type), siginfo_t(3type)

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                sigevent(3type)

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)