SIGEVENT(7)



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.   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  regis-
              tered 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  sig-
              info_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 implementa-
              tion 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  in-
              voked  with  sigev_value  as  its  sole  argument.  If sigev_no-
              tify_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),   getad-
       drinfo_a(3), lio_listio(3), mq_notify(3), aio(7), pthreads(7)

COLOPHON
       This  page  is  part of release 5.07 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                               2020-04-11                       SIGEVENT(7)

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