'\" te .\" Copyright (c) 2008, Sun Microsystems, Inc. All Rights Reserved. .\" Copyright 1989 AT&T .\" Portions Copyright (c) 1992, X/Open Company Limited. All Rights Reserved. .\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for permission to reproduce portions of its copyrighted documentation. Original documentation from The Open Group can be obtained online at http://www.opengroup.org/bookstore/. .\" The Institute of Electrical and Electronics Engineers and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase "this text" refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions 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. This notice shall appear on any product containing this material. .TH mq_notify 3C "5 Feb 2008" "SunOS 5.11" "Standard C Library Functions" .SH NAME mq_notify \- notify process (or thread) that a message is available on a queue .SH SYNOPSIS .LP .nf #include \fBint\fR \fBmq_notify\fR(\fBmqd_t\fR \fImqdes\fR, \fBconst struct sigevent *\fR\fInotification\fR); .fi .SH DESCRIPTION .sp .LP The \fBmq_notify()\fR function provides an asynchronous mechanism for processes to receive notice that messages are available in a message queue, rather than synchronously blocking (waiting) in \fBmq_receive\fR(3C). .sp .LP If \fInotification\fR is not \fINULL\fR, this function registers the calling process to be notified of message arrival at an empty message queue associated with the message queue descriptor, \fImqdes\fR. The notification specified by \fInotification\fR will be sent to the process when the message queue transitions from empty to non-empty. See \fBsignal.h\fR(3HEAD). At any time, only one process may be registered for notification by a specific 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 will fail. .sp .LP If \fInotification\fR is \fINULL\fR 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. .sp .LP When the notification is sent to the registered process, its registration is removed. The message queue is then available for registration. .sp .LP If a process has registered for notification of message arrival at a message queue and some processes is blocked in \fBmq_receive\fR(3C) waiting to receive a message when a message arrives at the queue, the arriving message will be received by the appropriate \fBmq_receive\fR(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. .sp .LP Any notification registration is removed if the calling process either closes the message queue or exits. .SH RETURN VALUES .sp .LP Upon successful completion, \fBmq_notify()\fR returns \fB0\fR; otherwise, it returns \fB\(mi1\fR and sets \fBerrno\fR to indicate the error. .SH ERRORS .sp .LP The \fBmq_notify()\fR function will fail if: .sp .ne 2 .mk .na \fB\fBEBADF\fR\fR .ad .RS 9n .rt The \fImqdes\fR argument is not a valid message queue descriptor. .RE .sp .ne 2 .mk .na \fB\fBEBUSY\fR\fR .ad .RS 9n .rt A process is already registered for notification by the message queue. .RE .SH ATTRIBUTES .sp .LP See \fBattributes\fR(5) for descriptions of the following attributes: .sp .sp .TS tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) . ATTRIBUTE TYPEATTRIBUTE VALUE _ Interface StabilityCommitted _ MT-LevelMT-Safe _ StandardSee \fBstandards\fR(5). .TE .SH SEE ALSO .sp .LP \fBmq_close\fR(3C), \fBmq_open\fR(3C), \fBmq_receive\fR(3C), \fBmq_send\fR(3C), \fBmqueue.h\fR(3HEAD), \fBsiginfo.h\fR(3HEAD), \fBsignal.h\fR(3HEAD), \fBattributes\fR(5), \fBstandards\fR(5)