Merge from vendor branch BZIP:
[dragonfly.git] / lib / libc / gen / msgget.3
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1.\" $NetBSD: msgget.2,v 1.1 1995/10/16 23:49:19 jtc Exp $
2.\"
3.\" Copyright (c) 1995 Frank van der Linden
4.\" All rights reserved.
5.\"
6.\" Redistribution and use in source and binary forms, with or without
7.\" modification, are permitted provided that the following conditions
8.\" are met:
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
20.\"
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.
31.\" $FreeBSD: src/lib/libc/gen/msgget.3,v 1.7.2.5 2003/03/15 15:11:05 trhodes Exp $
1de703da 32.\" $DragonFly: src/lib/libc/gen/msgget.3,v 1.2 2003/06/17 04:26:42 dillon Exp $
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33.\"
34.\"/
35.Dd August 17, 1995
36.Dt MSGGET 3
37.Os
38.Sh NAME
39.Nm msgget
40.Nd get message queue
41.Sh LIBRARY
42.Lb libc
43.Sh SYNOPSIS
44.In sys/types.h
45.In sys/ipc.h
46.In sys/msg.h
47.Ft int
48.Fn msgget "key_t key" "int msgflg"
49.Sh DESCRIPTION
50The
51.Fn msgget
52function
53returns the message queue identifier associated with
54.Fa key .
55A message queue identifier is a unique integer greater than zero.
56.Pp
57A message queue is created if either
58.Fa key
59is equal to
60.Dv IPC_PRIVATE ,
61or
62.Fa key
63does not have a message queue identifier associated with it, and the
64.Dv IPC_CREAT
65bit is set in
66.Fa msgflg .
67.Pp
68If a new message queue is created, the data structure associated with it (the
69.Va msqid_ds
70structure, see
71.Xr msgctl 3 )
72is initialized as follows:
73.Bl -bullet
74.It
75.Va msg_perm.cuid
76and
77.Va msg_perm.uid
78are set to the effective uid of the calling process.
79.It
80.Va msg_perm.gid
81and
82.Va msg_perm.cgid
83are set to the effective gid of the calling process.
84.It
85.Va msg_perm.mode
86is set to the lower 9 bits of
87.Fa msgflg .
88.It
89.Va msg_cbytes ,
90.Va msg_qnum ,
91.Va msg_lspid ,
92.Va msg_lrpid ,
93.Va msg_rtime ,
94and
95.Va msg_stime
96are set to 0.
97.It
98.Va msg_qbytes
99is set to the system wide maximum value for the number of bytes in a queue
100.Pf ( Dv MSGMNB ) .
101.It
102.Va msg_ctime
103is set to the current time.
104.El
105.Sh RETURN VALUES
106Upon successful completion a positive message queue identifier is returned.
107Otherwise, -1 is returned and the global variable
108.Va errno
109is set to indicate the error.
110.Sh ERRORS
111.Bl -tag -width Er
112.It Bq Er EACCES
113A message queue is already associated with
114.Fa key
115and the caller has no permission to access it.
116.It Bq Er EEXIST
117Both
118.Dv IPC_CREAT
119and
120.Dv IPC_EXCL
121are set in
122.Fa msgflg ,
123and a message queue is already associated with
124.Fa key .
125.It Bq Er ENOSPC
126A new message queue could not be created because the system limit for
127the number of message queues has been reached.
128.It Bq Er ENOENT
129.Dv IPC_CREAT
130was not set in
131.Fa msgflg
132and no message queue associated with
133.Fa key
134was found.
135.El
136.Sh SEE ALSO
137.Xr msgctl 3 ,
138.Xr msgrcv 3 ,
139.Xr msgsnd 3
140.Sh HISTORY
141Message queues appeared in the first release of
142.At V .