mq_notify(3) [netbsd man page]
MQ_NOTIFY(3) BSD Library Functions Manual MQ_NOTIFY(3) NAME
mq_notify -- notify process that a message is available (REALTIME) LIBRARY
POSIX Real-time Library (librt, -lrt) SYNOPSIS
#include <mqueue.h> int mq_notify(mqd_t mqdes, const struct sigevent *notification); DESCRIPTION
If the argument notification is not NULL, this function will register the calling process to be notified of message arrival at an empty mes- sage 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 notifi- cation 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 reg- istration. 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 behav- ior 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 indi- cate 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
mq(3), sigevent(3) 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 Elec- trical 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 . BSD
June 7, 2010 BSD
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mq_notify(3C) Standard C Library Functions mq_notify(3C) NAME
mq_notify - notify process (or thread) that a message is available on a queue SYNOPSIS
#include <mqueue.h> int mq_notify(mqd_t mqdes, const struct sigevent *notification); DESCRIPTION
The mq_notify() function provides an asynchronous mechanism for processes to receive notice that messages are available in a message queue, rather than synchronously blocking (waiting) in mq_receive(3C). If notification is not NULL, this function registers the calling process to be notified of message arrival at an empty message queue asso- ciated with the message queue descriptor, mqdes. The notification specified by notification will be sent to the process when the message queue transitions from empty to non-empty. See signal.h(3HEAD). At any time, only one process may be registered for notification by a spe- cific message queue. If the calling process or any other process has already registered for notification of message arrival at the speci- fied message queue, subsequent attempts to register for that message queue will fail. If notification is NULL and the process is currently registered for notification by the specified message queue, the existing registration is removed. The message queue is then available for future registration. When the notification is sent to the registered process, its registration is removed. The message queue is then available for registration. If a process has registered for notification of message arrival at a message queue and some processes is blocked in mq_receive(3C) waiting to receive a message when a message arrives at the queue, the arriving message will be received by the appropriate mq_receive(3C), and no notification will be sent to the registered process. The resulting behavior is as if the message queue remains empty, and this notification will not be sent until the next arrival of a message at this queue. Any notification registration is removed if the calling process either closes the message queue or exits. RETURN VALUES
Upon successful completion, mq_notify() returns 0; otherwise, it returns -1 and sets errno to indicate the error. ERRORS
The mq_notify() function will fail if: EBADF The mqdes argument is not a valid message queue descriptor. EBUSY A process is already registered for notification by the message queue. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Committed | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ |Standard |See standards(5). | +-----------------------------+-----------------------------+ SEE ALSO
mq_close(3C), mq_open(3C), mq_receive(3C), mq_send(3C), mqueue.h(3HEAD), siginfo.h(3HEAD), signal.h(3HEAD), attributes(5), standards(5) SunOS 5.11 5 Feb 2008 mq_notify(3C)