2 .\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
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.
15 .\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
16 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 .\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
19 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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26 .\" $FreeBSD: src/lib/libc/sys/semctl.2,v 1.9.2.6 2002/03/11 08:37:47 maxim Exp $
33 .Nd control operations on a semaphore set
41 .Fn semctl "int semid" "int semnum" "int cmd" ...
44 performs the operation indicated by
46 on the semaphore set indicated by
49 .Fa "union semun arg" ,
50 is required for certain values of
52 For the commands that use the
56 is defined as follows:
62 int val; /* value for SETVAL */
63 struct semid_ds *buf; /* buffer for IPC_STAT & IPC_SET */
64 u_short *array; /* array for GETALL & SETALL */
68 Commands are performed as follows:
70 .\" This section based on Stevens, _Advanced Programming in the UNIX
73 .Bl -tag -width ".Dv IPC_RMID"
75 Fetch the semaphore set's
76 .Fa "struct semid_ds" ,
77 storing it in the memory pointed to by
85 members of the semaphore set's
87 to match those of the struct pointed to by
89 The calling process's effective uid must
94 or it must have superuser privileges.
96 Immediately removes the semaphore set from the system.
97 The calling process's effective uid must equal the semaphore set's
101 or the process must have superuser privileges.
103 Return the value of semaphore number
106 Set the value of semaphore number
111 Return the pid of the last process to perform an operation on
115 Return the number of processes waiting for semaphore number
117 value to become greater than its current value.
119 Return the number of processes waiting for semaphore number
123 Fetch the value of all of the semaphores in the set into the
127 Set the values of all of the semaphores in the set to the values
128 in the array pointed to by
133 .Fa "struct semid_ds"
134 is defined as follows:
137 .\" Taken straight from <sys/sem.h>.
140 struct ipc_perm sem_perm; /* operation permission struct */
141 struct sem *sem_base; /* pointer to first semaphore in set */
142 u_short sem_nsems; /* number of sems in set */
143 time_t sem_otime; /* last operation time */
144 long sem_pad1; /* SVABI/386 says I need this here */
145 time_t sem_ctime; /* last change time */
146 /* Times measured in secs since */
147 /* 00:00:00 GMT, Jan. 1, 1970 */
148 long sem_pad2; /* SVABI/386 says I need this here */
149 long sem_pad3[4]; /* SVABI/386 says I need this here */
156 .Dv GETVAL , GETPID , GETNCNT
160 returns the corresponding value; otherwise, 0 is returned.
161 On failure, -1 is returned, and
163 is set to indicate the error.
165 The XSI Interprocess Communication family of functions is also available
166 as an implementation in userspace.
169 daemon has to be running.
173 variable is set in a process' environment, the process and its children
174 will use the userspace implementation.
180 No semaphore set corresponds to
184 is not in the range of valid semaphores for given semaphore set.
186 The calling process's effective uid does not match the uid of
187 the semaphore set's owner or creator.
189 Permission denied due to mismatch between operation and mode of
199 specific userspace implementation (see