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); Linux-specific */
       };

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 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).

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  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
       https://www.kernel.org/doc/man-pages/.

GNU                                                2020-11-01                                        SIGEVENT(7)