152 lines
4 KiB
Groff
152 lines
4 KiB
Groff
|
.\" $NetBSD: msgget.2,v 1.14 2004/05/13 10:20:58 wiz 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.
|
||
|
|
.\"
|
||
|
|
.Dd May 13, 2004
|
||
|
|
.Dt MSGGET 2
|
||
|
|
.Os
|
||
|
|
.Sh NAME
|
||
|
|
.Nm msgget
|
||
|
|
.Nd get message queue identifier
|
||
|
|
.Sh LIBRARY
|
||
|
|
.Lb libc
|
||
|
|
.Sh SYNOPSIS
|
||
|
|
.In sys/msg.h
|
||
|
|
.Ft int
|
||
|
|
.Fn msgget "key_t key" "int msgflg"
|
||
|
|
.Sh DESCRIPTION
|
||
|
|
The
|
||
|
|
.Fn msgget
|
||
|
|
system call 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 .
|
||
|
|
If both the
|
||
|
|
.Dv IPC_CREAT
|
||
|
|
bit and the
|
||
|
|
.Dv IPC_EXCL
|
||
|
|
bit are set in
|
||
|
|
.Fa msgflg ,
|
||
|
|
and
|
||
|
|
.Fa key
|
||
|
|
has a message queue identifier associated with it already,
|
||
|
|
the operation will fail.
|
||
|
|
.Pp
|
||
|
|
If a new message queue is created, the data structure associated with it (the
|
||
|
|
.Va msqid_ds
|
||
|
|
structure, see
|
||
|
|
.Xr msgctl 2 )
|
||
|
|
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_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
|
||
|
|
.Pq 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
|
||
|
|
is not set in
|
||
|
|
.Fa msgflg
|
||
|
|
and no message queue associated with
|
||
|
|
.Fa key
|
||
|
|
was found.
|
||
|
|
.El
|
||
|
|
.Sh SEE ALSO
|
||
|
|
.Xr msgctl 2 ,
|
||
|
|
.Xr msgrcv 2 ,
|
||
|
|
.Xr msgsnd 2 ,
|
||
|
|
.Xr ftok 3
|
||
|
|
.Sh STANDARDS
|
||
|
|
The
|
||
|
|
.Nm
|
||
|
|
system call conforms to
|
||
|
|
.St -xsh5 .
|
||
|
|
.Sh HISTORY
|
||
|
|
Message queues appeared in the first release of
|
||
|
|
.At V .
|