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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 no-
tified 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 sigac-
tion(2) SA_SIGINFO flag, then the following fields are set in the siginfo_t struc-
ture 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 noti-
fication.
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 sigwait-
info(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)
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