1.\" $OpenBSD: msgget.2,v 1.12 2014/02/12 16:46:29 schwarze Exp $ 2.\" $NetBSD: msgget.2,v 1.1 1995/10/16 23:49:19 jtc Exp $ 3.\" 4.\" Copyright (c) 1995 Frank van der Linden 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed for the NetBSD Project 18.\" by Frank van der Linden 19.\" 4. The name of the author may not be used to endorse or promote products 20.\" derived from this software without specific prior written permission 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32.\"/ 33.Dd $Mdocdate: February 12 2014 $ 34.Dt MSGGET 2 35.Os 36.Sh NAME 37.Nm msgget 38.Nd get message queue 39.Sh SYNOPSIS 40.Fd #include <sys/types.h> 41.Fd #include <sys/ipc.h> 42.Fd #include <sys/msg.h> 43.Ft int 44.Fn msgget "key_t key" "int msgflg" 45.Sh DESCRIPTION 46.Fn msgget 47returns the message queue identifier associated with 48.Fa key . 49A message queue identifier is a unique integer greater than zero. 50.Pp 51A message queue is created if either 52.Fa key 53is equal to 54.Dv IPC_PRIVATE , 55or 56.Fa key 57does not have a message queue identifier associated with it, and the 58.Dv IPC_CREAT 59bit is set in 60.Fa msgflg . 61.Pp 62If a new message queue is created, the data structure associated with it (the 63.Va msqid_ds 64structure, see 65.Xr msgctl 2 ) 66is initialized as follows: 67.Bl -bullet 68.It 69.Va msg_perm.cuid 70and 71.Va msg_perm.uid 72are set to the effective UID of the calling process. 73.It 74.Va msg_perm.gid 75and 76.Va msg_perm.cgid 77are set to the effective GID of the calling process. 78.It 79.Va msg_perm.mode 80is set to the lower 9 bits of 81.Fa msgflg . 82.It 83.Va msg_cbytes , 84.Va msg_qnum , 85.Va msg_lspid , 86.Va msg_lrpid , 87.Va msg_rtime , 88and 89.Va msg_stime 90are set to 0. 91.It 92.Va msg_qbytes 93is set to the system wide maximum value for the number of bytes in a queue 94.Pq Dv MSGMNB . 95.It 96.Va msg_ctime 97is set to the current time. 98.El 99.Sh RETURN VALUES 100Upon successful completion a positive message queue identifier is returned. 101Otherwise, \-1 is returned and the global variable 102.Va errno 103is set to indicate the error. 104.Sh ERRORS 105.Bl -tag -width Er 106.It Bq Er EACCES 107A message queue is already associated with 108.Fa key 109and the caller has no permission to access it. 110.It Bq Er EEXIST 111Both 112.Dv IPC_CREAT 113and 114.Dv IPC_EXCL 115are set in 116.Fa msgflg , 117and a message queue is already associated with 118.Fa key . 119.It Bq Er ENOSPC 120A new message queue could not be created because the system limit for 121the number of message queues has been reached. 122.It Bq Er ENOENT 123.Dv IPC_CREAT 124was not set in 125.Fa msgflg 126and no message queue associated with 127.Fa key 128was found. 129.El 130.Sh SEE ALSO 131.Xr msgctl 2 , 132.Xr msgrcv 2 , 133.Xr msgsnd 2 , 134.Xr ftok 3 135.Sh HISTORY 136Message queues appeared in 137.At V.1 . 138