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)