.\" $NetBSD: msgget.2,v 1.1 1995/10/16 23:49:19 jtc Exp $ .\" .\" Copyright (c) 1995 Frank van der Linden .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed for the NetBSD Project .\" by Frank van der Linden .\" 4. The name of the author may not be used to endorse or promote products .\" derived from this software without specific prior written permission .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" $FreeBSD: src/lib/libc/gen/msgget.3,v 1.12 2001/10/01 16:08:51 ru Exp $ .\" .\"/ .Dd August 17, 1995 .Dt MSGGET 3 .Os .Sh NAME .Nm msgget .Nd get message queue .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In sys/types.h .In sys/ipc.h .In sys/msg.h .Ft int .Fn msgget "key_t key" "int msgflg" .Sh DESCRIPTION .Fn msgget returns the message queue identifier associated with .Fa key . A message queue identifier is a unique integer greater than zero. .Pp A message queue is created if either .Fa key is equal to .Dv IPC_PRIVATE , or .Fa key does not have a message queue identifier associated with it, and the .Dv IPC_CREAT bit is set in .Fa msgflg . .Pp If a new message queue is created, the data structure associated with it (the .Va msqid_ds structure, see .Xr msgctl 3 ) is initialized as follows: .Bl -bullet .It .Va msg_perm.cuid and .Va msg_perm.uid are set to the effective uid of the calling process. .It .Va msg_perm.gid and .Va msg_perm.cgid are set to the effective gid of the calling process. .It .Va msg_perm.mode is set to the lower 9 bits of .Fa msgflg . .It .Va msg_cbytes , .Va msg_qnum , .Va msg_lspid , .Va msg_lrpid , .Va msg_rtime , and .Va msg_stime are set to 0. .It .Va msg_qbytes is set to the system wide maximum value for the number of bytes in a queue .Pf ( Dv MSGMNB ) . .It .Va msg_ctime is set to the current time. .El .Sh RETURN VALUES Upon successful completion a positive message queue identifier is returned. Otherwise, -1 is returned and the global variable .Va errno is set to indicate the error. .Sh ERRORS .Bl -tag -width Er .It Bq Er EACCES A message queue is already associated with .Fa key and the caller has no permission to access it. .It Bq Er EEXIST Both .Dv IPC_CREAT and .Dv IPC_EXCL are set in .Fa msgflg , and a message queue is already associated with .Fa key . .It Bq Er ENOSPC A new message queue could not be created because the system limit for the number of message queues has been reached. .It Bq Er ENOENT .Dv IPC_CREAT was not set in .Fa msgflg and no message queue associated with .Fa key was found. .El .Sh SEE ALSO .Xr msgctl 3 , .Xr msgrcv 3 , .Xr msgsnd 3 .Sh HISTORY Message queues appeared in the first release of .At V .