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
24 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 .\" $FreeBSD: src/lib/libc/sys/semget.2,v 1.7.2.5 2001/12/14 18:34:01 ru Exp $
33 .Nd obtain a semaphore id
41 .Fn semget "key_t key" "int nsems" "int flag"
43 Based on the values of
48 returns the identifier of a newly created or previously existing
51 .\" This is copied verbatim from the shmget manpage. Perhaps
52 .\" it should go in a common manpage, such as .Xr ipc 2
55 is analogous to a filename: it provides a handle that names an
57 There are three ways to specify a key:
61 may be specified, in which case a new IPC object will be created.
63 An integer constant may be specified.
64 If no IPC object corresponding to
70 a new one will be created.
73 may be used to generate a key from a pathname.
78 .\" Likewise for this section, except SHM_* becomes SEM_*.
81 The mode of a newly created IPC object is determined by
83 the following constants into the
86 .Bl -tag -width XSEM_WXX6XXX
90 Alter access for user.
92 Read access for group.
94 Alter access for group.
96 Read access for other.
98 Alter access for other.
101 If a new set of semaphores is being created,
103 is used to indicate the number of semaphores the set should contain.
106 may be specified as 0.
109 returns the id of a semaphore set if successful; otherwise, -1
112 is set to indicate the error.
114 The XSI Interprocess Communication family of functions is also available
115 as an implementation in userspace.
118 daemon has to be running.
122 variable is set in a process' environment, the process and its children
123 will use the userspace implementation.
128 .\" ipcperm could fail (we're opening to read and write, as it were)
130 Access permission failure.
132 .\" sysv_sem.c is quite explicit about these, so I'm pretty sure
139 were specified, and a semaphore set corresponding to
143 The number of semaphores requested exceeds the system imposed maximum
146 Insufficiently many semaphores are available.
148 The kernel could not allocate a
149 .Fa "struct semid_ds" .
151 No semaphore set was found corresponding to