sigevent — structure for notification from asynchronous routines
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#include <signal.h>
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| union | sigval { |
/* Data passed with notification */
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| int | sival_int; |
/* Integer value */
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| void | * | sival_ptr; |
/* Pointer value */
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| }; | ||||
| struct | sigevent { | |||
| int | sigev_notify; |
/* Notification method */
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| int | sigev_signo; |
/* Notification signal */
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| union sigval | sigev_value; |
/* Data passed with notification */
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| void | (* | sigev_notify_function)(union sigval); |
/* Function used for thread
notification (SIGEV_THREAD) */ |
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| void | * | sigev_notify_attributes; |
/* Attributes for notification thread
(SIGEV_THREAD) */ |
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| pid_t | sigev_notify_thread_id; |
/* ID of thread to signal
(SIGEV_THREAD_ID); Linux-specific */ |
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| }; | ||||
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_NONEA "null" notification: don't do anything when the event occurs.
SIGEV_SIGNALNotify 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_codeThis field is set to a value that depends on the API delivering the notification.
si_signoThis field is set to the signal number (i.e., the same value as in
sigev_signo).si_valueThis 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_THREADNotify 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).
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)