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

       sigevent - structure for notification from asynchronous routines

       #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 */

       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

       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 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).

              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).

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

       This page is part of release 5.10 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                                2020-11-01                        SIGEVENT(7)