1 .\" $NetBSD: msgctl.2,v 1.1 1995/10/16 23:49:15 jtc Exp $
3 .\" Copyright (c) 1995 Frank van der Linden
4 .\" All rights reserved.
6 .\" Redistribution and use in source and binary forms, with or without
7 .\" modification, are permitted provided that the following conditions
9 .\" 1. Redistributions of source code must retain the above copyright
10 .\" notice, this list of conditions and the following disclaimer.
11 .\" 2. Redistributions in binary form must reproduce the above copyright
12 .\" notice, this list of conditions and the following disclaimer in the
13 .\" documentation and/or other materials provided with the distribution.
14 .\" 3. All advertising materials mentioning features or use of this software
15 .\" must display the following acknowledgement:
16 .\" This product includes software developed for the NetBSD Project
17 .\" by Frank van der Linden
18 .\" 4. The name of the author may not be used to endorse or promote products
19 .\" derived from this software without specific prior written permission
21 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 .Nd message control operations
45 .Fn msgctl "int msqid" "int cmd" "struct msqid_ds *buf"
49 system call performs some control operations on the message queue specified
53 Each message queue has a data structure associated with it, parts of which
56 and parts of which determine the actions of
58 The data structure is defined in
60 and contains (amongst others) the following members:
63 struct ipc_perm msg_perm; /* msg queue permission bits */
64 msglen_t msg_cbytes; /* number of bytes in use on the queue */
65 msgqnum_t msg_qnum; /* number of msgs in the queue */
66 msglen_t msg_qbytes; /* max # of bytes on the queue */
67 pid_t msg_lspid; /* pid of last msgsnd() */
68 pid_t msg_lrpid; /* pid of last msgrcv() */
69 time_t msg_stime; /* time of last msgsnd() */
70 time_t msg_rtime; /* time of last msgrcv() */
71 time_t msg_ctime; /* time of last msgctl() */
77 structure used inside the
79 structure is defined in
84 uid_t cuid; /* creator user id */
85 gid_t cgid; /* creator group id */
86 uid_t uid; /* user id */
87 gid_t gid; /* group id */
88 mode_t mode; /* r/w permission */
89 unsigned short seq; /* sequence # (to generate unique ipcid) */
90 key_t key; /* user specified msg/sem/shm key */
94 The operation to be performed by
99 .Bl -tag -width IPC_RMIDX
101 Gather information about the message queue and place it in the
102 structure pointed to by
111 fields in the structure associated with
113 The values are taken from the corresponding fields in the structure
116 This operation can only be executed by the super-user, or a process that
117 has an effective user id equal to either
121 in the data structure associated with the message queue.
124 can only be increased by the super-user.
127 that exceed the system limit (MSGMNB from
129 are silently truncated to that limit.
131 Remove the message queue specified by
133 and destroy the data associated with it.
134 Only the super-user or a process
135 with an effective uid equal to the
139 values in the data structure associated with the queue can do this.
142 The permission to read from or write to a message queue (see
148 field in the same way as is
151 but the effective uid can match either the
156 effective gid can match either
172 is equal to IPC_SET or IPC_RMID and the caller is not the super-user, nor does
173 the effective uid match either the
177 fields of the data structure associated with the message queue.
179 An attempt is made to increase the value of
182 but the caller is not the super-user.
184 The command is IPC_STAT
185 and the caller has no read permission for this message queue.
190 is not a valid message queue identifier.
193 is not a valid command.
198 specifies an invalid address.
205 Message queues appeared in the first release of