MQ_NOTIFY(3) | Library Functions Manual | MQ_NOTIFY(3) |
mq_notify
—
#include <mqueue.h>
int
mq_notify
(mqd_t
mqdes, const struct
sigevent *notification);
NULL
, this function will register the calling process
to be notified of message arrival at an empty message queue associated with
the specified message queue descriptor, mqdes. The
notification specified by the notification argument will
be sent to the process when the message queue transitions from empty to
non-empty. At any time, only one process may be registered for notification by
a message queue. If the calling process or any other process has already
registered for notification of message arrival at the specified message queue,
subsequent attempts to register for that message queue fails.
If notification is
NULL
and the process is currently registered for
notification by the specified message queue, the existing registration will
be removed.
When the notification is sent to the registered process, its registration will be removed. The message queue will then be available for registration.
If a process has registered for notification of message arrival at
a message queue and some thread is blocked in
mq_receive
() waiting to receive a message when a
message arrives at the queue, the arriving message will satisfy the
appropriate mq_receive
(). The resulting behavior is
as if the message queue remains empty, and no notification will be sent.
mq_notify
() function returns the value 0 if
successful; otherwise the value -1 is returned and the global variable
errno is set to indicate the error.
mq_notify
() function fails if:
June 7, 2010 | NetBSD 9.0 |