sigevent(3type)                                                sigevent(3type)

NAME
       sigevent, sigval - structure for notification from asynchronous
       routines

SYNOPSIS
       #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
   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
       POSIX.1-2008.

HISTORY
       POSIX.1-2001.

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

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

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

Linux man-pages 6.7               2023-10-31                   sigevent(3type)