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

NAME

       sigevent - structure for notification from asynchronous routines

SYNOPSIS

       #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) */
       };

DESCRIPTION

       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 asyn-
       chronous 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.   Pro-
       grams 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 cre-
               ated 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).

SEE ALSO

       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)

COLOPHON

       This  page is part of release 4.15 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 https://www.kernel.org/doc/man-pages/.

GNU                                                                 2017-07-13                                                         SIGEVENT(7)