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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 notified about an event (e.g., completion of an asynchronous request, expi‐
ration 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 sig‐
info_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 at‐
tributes 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)
GNU 2021-03-22 SIGEVENT(7)