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) */

       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

               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

               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 5.05 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                               2017-07-13                       SIGEVENT(7)