142 lines
3.9 KiB
Groff
142 lines
3.9 KiB
Groff
.\" $NetBSD: msgget.2,v 1.9 2001/09/16 02:13:29 wiz Exp $
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.\"
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.\" Copyright (c) 1995 Frank van der Linden
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed for the NetBSD Project
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.\" by Frank van der Linden
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd August 25, 1999
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.Dt MSGGET 2
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.Os
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.Sh NAME
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.Nm msgget
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.Nd get message queue identifier
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.Fd #include <sys/msg.h>
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.Ft int
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.Fn msgget "key_t key" "int msgflg"
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.Sh DESCRIPTION
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The
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.Fn msgget
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system call returns the message queue identifier associated with
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.Fa key .
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A message queue identifier is a unique integer greater than zero.
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.Pp
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A message queue is created if either
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.Fa key
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is equal to
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.Dv IPC_PRIVATE ,
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or
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.Fa key
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does not have a message queue identifier associated with it and the
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.Dv IPC_CREAT
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bit is set in
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.Fa msgflg .
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.Pp
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If a new message queue is created, the data structure associated with it (the
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.Va msqid_ds
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structure, see
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.Xr msgctl 2 )
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is initialized as follows:
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.Bl -bullet
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.It
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.Va msg_perm.cuid
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and
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.Va msg_perm.uid
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are set to the effective uid of the calling process.
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.It
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.Va msg_perm.gid
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and
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.Va msg_perm.cgid
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are set to the effective gid of the calling process.
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.It
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.Va msg_perm.mode
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is set to the lower 9 bits of
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.Fa msgflg .
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.It
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.Va msg_qnum ,
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.Va msg_lspid ,
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.Va msg_lrpid ,
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.Va msg_rtime ,
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and
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.Va msg_stime
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are set to 0.
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.It
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.Va msg_qbytes
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is set to the system wide maximum value for the number of bytes in a queue
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.Pq Dv MSGMNB .
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.It
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.Va msg_ctime
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is set to the current time.
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.El
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.Sh RETURN VALUES
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Upon successful completion a positive message queue identifier is returned.
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Otherwise, -1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EACCES
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A message queue is already associated with
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.Fa key
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and the caller has no permission to access it.
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.It Bq Er EEXIST
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Both
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.Dv IPC_CREAT
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and
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.Dv IPC_EXCL
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are set in
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.Fa msgflg ,
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and a message queue is already associated with
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.Fa key .
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.It Bq Er ENOSPC
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A new message queue could not be created because the system limit for
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the number of message queues has been reached.
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.It Bq Er ENOENT
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.Dv IPC_CREAT
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is not set in
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.Fa msgflg
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and no message queue associated with
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.Fa key
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was found.
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.El
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.Sh SEE ALSO
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.Xr msgctl 2 ,
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.Xr msgrcv 2 ,
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.Xr msgsnd 2 ,
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.Xr ftok 3
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.Sh STANDARDS
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The
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.Nm
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system call conforms to
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.St -xsh5 .
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.Sh HISTORY
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Message queues appeared in the first release of
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.At V .
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