1.\" $NetBSD: msgget.2,v 1.10 2002/02/08 01:28:19 ross 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.\" 32.Dd August 25, 1999 33.Dt MSGGET 2 34.Os 35.Sh NAME 36.Nm msgget 37.Nd get message queue identifier 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.Fd #include \*[Lt]sys/msg.h\*[Gt] 42.Ft int 43.Fn msgget "key_t key" "int msgflg" 44.Sh DESCRIPTION 45The 46.Fn msgget 47system call returns 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_qnum , 84.Va msg_lspid , 85.Va msg_lrpid , 86.Va msg_rtime , 87and 88.Va msg_stime 89are set to 0. 90.It 91.Va msg_qbytes 92is set to the system wide maximum value for the number of bytes in a queue 93.Pq Dv MSGMNB . 94.It 95.Va msg_ctime 96is set to the current time. 97.El 98.Sh RETURN VALUES 99Upon successful completion a positive message queue identifier is returned. 100Otherwise, -1 is returned and the global variable 101.Va errno 102is set to indicate the error. 103.Sh ERRORS 104.Bl -tag -width Er 105.It Bq Er EACCES 106A message queue is already associated with 107.Fa key 108and the caller has no permission to access it. 109.It Bq Er EEXIST 110Both 111.Dv IPC_CREAT 112and 113.Dv IPC_EXCL 114are set in 115.Fa msgflg , 116and a message queue is already associated with 117.Fa key . 118.It Bq Er ENOSPC 119A new message queue could not be created because the system limit for 120the number of message queues has been reached. 121.It Bq Er ENOENT 122.Dv IPC_CREAT 123is not set in 124.Fa msgflg 125and no message queue associated with 126.Fa key 127was found. 128.El 129.Sh SEE ALSO 130.Xr msgctl 2 , 131.Xr msgrcv 2 , 132.Xr msgsnd 2 , 133.Xr ftok 3 134.Sh STANDARDS 135The 136.Nm 137system call conforms to 138.St -xsh5 . 139.Sh HISTORY 140Message queues appeared in the first release of 141.At V . 142