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.\" $FreeBSD$ 32.\" 33.\"/ 34.Dd July 9, 2009 35.Dt MSGGET 2 36.Os 37.Sh NAME 38.Nm msgget 39.Nd get message queue 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In sys/types.h 44.In sys/ipc.h 45.In sys/msg.h 46.Ft int 47.Fn msgget "key_t key" "int msgflg" 48.Sh DESCRIPTION 49The 50.Fn msgget 51function 52returns the message queue identifier associated with 53.Fa key . 54A message queue identifier is a unique integer greater than zero. 55.Pp 56A message queue is created if either 57.Fa key 58is equal to 59.Dv IPC_PRIVATE , 60or 61.Fa key 62does not have a message queue identifier associated with it, and the 63.Dv IPC_CREAT 64bit is set in 65.Fa msgflg . 66.Pp 67If a new message queue is created, the data structure associated with it (the 68.Va msqid_ds 69structure, see 70.Xr msgctl 2 ) 71is initialized as follows: 72.Bl -bullet 73.It 74.Va msg_perm.cuid 75and 76.Va msg_perm.uid 77are set to the effective uid of the calling process. 78.It 79.Va msg_perm.gid 80and 81.Va msg_perm.cgid 82are set to the effective gid of the calling process. 83.It 84.Va msg_perm.mode 85is set to the lower 9 bits of 86.Fa msgflg . 87.It 88.Va msg_cbytes , 89.Va msg_qnum , 90.Va msg_lspid , 91.Va msg_lrpid , 92.Va msg_rtime , 93and 94.Va msg_stime 95are set to 0. 96.It 97.Va msg_qbytes 98is set to the system wide maximum value for the number of bytes in a queue 99.Pf ( Dv MSGMNB ) . 100.It 101.Va msg_ctime 102is set to the current time. 103.El 104.Sh RETURN VALUES 105Upon successful completion a positive message queue identifier is returned. 106Otherwise, -1 is returned and the global variable 107.Va errno 108is set to indicate the error. 109.Sh ERRORS 110.Bl -tag -width Er 111.It Bq Er EACCES 112A message queue is already associated with 113.Fa key 114and the caller has no permission to access it. 115.It Bq Er EEXIST 116Both 117.Dv IPC_CREAT 118and 119.Dv IPC_EXCL 120are set in 121.Fa msgflg , 122and a message queue is already associated with 123.Fa key . 124.It Bq Er ENOSPC 125A new message queue could not be created because the system limit for 126the number of message queues has been reached. 127.It Bq Er ENOENT 128.Dv IPC_CREAT 129was not set in 130.Fa msgflg 131and no message queue associated with 132.Fa key 133was found. 134.El 135.Sh SEE ALSO 136.Xr msgctl 2 , 137.Xr msgrcv 2 , 138.Xr msgsnd 2 139.Sh HISTORY 140Message queues appeared in the first release of 141.At V . 142