sigevent(7) - man - phpMan

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); Linux-specific */
       };

DESCRIPTION
       The  sigevent  structure is used by various APIs to describe the way a process is to be noti‐
       fied 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  rele‐
       vant 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  sigac‐‐
              tion(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  notifi‐
                        cation.

              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  func‐
              tion  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)