1 .\" Copyright (c) 2005 David Xu <davidxu@FreeBSD.org>
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice(s), this list of conditions and the following disclaimer as
9 .\" the first lines of this file unmodified other than the possible
10 .\" addition of one or more copyright notices.
11 .\" 2. Redistributions in binary form must reproduce the above copyright
12 .\" notice(s), this list of conditions and the following disclaimer in
13 .\" the documentation and/or other materials provided with the
16 .\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
17 .\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
20 .\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
23 .\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24 .\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
25 .\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
26 .\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 .\" Portions of this text are reprinted and reproduced in electronic form
29 .\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
30 .\" Portable Operating System Interface (POSIX), The Open Group Base
31 .\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
32 .\" Electrical and Electronics Engineers, Inc and The Open Group. In the
33 .\" event of any discrepancy between this version and the original IEEE and
34 .\" The Open Group Standard, the original IEEE and The Open Group Standard is
35 .\" the referee document. The original Standard can be obtained online at
36 .\" http://www.opengroup.org/unix/online.html.
45 .Nd "notify process that a message is available (REALTIME)"
51 .Fn mq_notify "mqd_t mqdes" "const struct sigevent *notification"
53 If the argument notification is not
55 this system call will register the calling process to be notified of message
56 arrival at an empty message queue associated with the specified message
59 The notification specified by the
61 argument will be sent to
62 the process when the message queue transitions from empty to non-empty.
63 At any time, only one process may be registered for notification by a
65 If the calling process or any other process has already
66 registered for notification of message arrival at the specified message
67 queue, subsequent attempts to register for that message queue will fail.
73 structure that defines how the calling process will be notified.
75 .Fa notification->sigev_notify
78 then no signal will be posted, but the error status and the return status
79 for the operation will be set appropriately.
81 .Fa notification->sigev_notify
84 then the signal specified in
85 .Fa notification->sigev_signo
86 will be sent to the process.
87 The signal will be queued to the process and the value specified in
88 .Fa notification->sigev_value
91 component of the generated signal.
97 and the process is currently registered for notification by the specified
98 message queue, the existing registration will be removed.
100 When the notification is sent to the registered process, its registration
102 The message queue then is available for registration.
104 If a process has registered for notification of message arrival at a
105 message queue and some thread is blocked in
107 waiting to receive a message when a message arrives at the queue, the
108 arriving message will satisfy the appropriate
110 The resulting behavior is as if the message queue remains empty, and no
111 notification will be sent.
123 argument is not a valid message queue descriptor.
125 Process is already registered for notification by the message queue.
135 system call conforms to
140 message queues first appeared in
143 Portions of this text are reprinted and reproduced in electronic form
144 from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
145 Portable Operating System Interface (POSIX), The Open Group Base
146 Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
147 Electrical and Electronics Engineers, Inc and The Open Group. In the
148 event of any discrepancy between this version and the original IEEE and
149 The Open Group Standard, the original IEEE and The Open Group Standard is
150 the referee document. The original Standard can be obtained online at
151 http://www.opengroup.org/unix/online.html.