sigevent(7)
NAME
sigevent - structure for notification from asynchronous routines
SYNOPSIS
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
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 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
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 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 4.09 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/.
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