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SIGEVENT(7)                Linux Programmer's ManualSIGEVENT(7)NAME       sigevent - structure for notification from asynchronous routinesSYNOPSIS       #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 thesigaction(2) SA_SIGINFO flag, then the follow-               ing 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 ac-               cepted usingsigwaitinfo(2).       SIGEV_THREAD               Notify the process by invoking sigev_notify_function "as if" it               were  the start function of a new thread.  (Among the implemen-               tation 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_no-               tify_attributes  is  not   NULL,   it   should   point   to   a               pthread_attr_t  structure  that  defines attributes for the new               thread (seepthread_attr_init(3)).       SIGEV_THREAD_ID (Linux-specific)               Currently used only by POSIX timers; seetimer_create(2).SEE ALSOtimer_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 5.05 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       https://www.kernel.org/doc/man-pages/.GNU                               2017-07-13SIGEVENT(7)