NAME
mq_notify —
notify process that a message is
available (REALTIME)
LIBRARY
library “librt”
SYNOPSIS
#include
<mqueue.h>
int
mq_notify(mqd_t
mqdes, const struct
sigevent *notification);
DESCRIPTION
If the argument notification is notNULL, 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.
RETURN VALUES
The 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.
ERRORS
The mq_notify() function fails if:
- [
EBADF] - The mqdes argument is not a valid message queue descriptor.
- [
EBUSY] - A process is already registered for notification by the message queue.
SEE ALSO
STANDARDS
This function conforms to the IEEE Std 1003.1-2001 (“POSIX.1”) standard.
HISTORY
This function first appeared in NetBSD 5.0.
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html.