2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
200 lines
5.5 KiB
Groff
200 lines
5.5 KiB
Groff
.\" $NetBSD: msgctl.2,v 1.15 2010/03/22 19:30:55 joerg 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 MSGCTL 2
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.Os
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.Sh NAME
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.Nm msgctl
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.Nd message control operations
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/msg.h
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.Ft int
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.Fn msgctl "int msqid" "int cmd" "struct msqid_ds *buf"
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.Sh DESCRIPTION
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The
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.Fn msgctl
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system call performs control operations on the message queue specified
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by
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.Fa msqid .
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.Pp
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Each message queue has a
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.Sy msqid_ds
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structure associated with it which contains the following members:
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.Bd -literal
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struct ipc_perm msg_perm; /* msg queue permission bits */
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msgqnum_t msg_qnum; /* # of msgs in the queue */
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msglen_t msg_qbytes; /* max # of bytes on the queue */
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pid_t msg_lspid; /* pid of last msgsnd() */
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pid_t msg_lrpid; /* pid of last msgrcv() */
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time_t msg_stime; /* time of last msgsnd() */
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time_t msg_rtime; /* time of last msgrcv() */
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time_t msg_ctime; /* time of last msgctl() */
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.Ed
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.Pp
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The
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.Sy ipc_perm
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structure used inside the
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.Sy msgid_ds
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structure is defined in
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.In sys/ipc.h
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and contains the following members:
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.Bd -literal
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uid_t cuid; /* creator user id */
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gid_t cgid; /* creator group id */
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uid_t uid; /* user id */
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gid_t gid; /* group id */
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mode_t mode; /* permission (lower 9 bits) */
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.Ed
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.Pp
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The operation to be performed by
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.Fn msgctl
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is specified in
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.Fa cmd
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and is one of:
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.Bl -tag -width IPC_RMIDX
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.It Dv IPC_STAT
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Gather information about the message queue and place it in the
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structure pointed to by
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.Fa buf .
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.It Dv IPC_SET
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Set the value of the
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.Va msg_perm.uid ,
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.Va msg_perm.gid ,
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.Va msg_perm.mode
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and
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.Va msg_qbytes
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fields in the structure associated with
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.Fa msqid .
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The values are taken from the corresponding fields in the structure
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pointed to by
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.Fa buf .
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This operation can only be executed by the super-user, or a process that
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has an effective user id equal to either
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.Va msg_perm.cuid
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or
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.Va msg_perm.uid
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in the data structure associated with the message queue.
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The value of
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.Va msg_qbytes
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can only be increased by the super-user.
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Values for
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.Va msg_qbytes
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that exceed the system limit
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.Pf ( Dv MSGMNB
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from
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.In sys/msg.h )
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are silently truncated to that limit.
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.It Dv IPC_RMID
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Remove the message queue specified by
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.Fa msqid
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and destroy the data associated with it.
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Only the super-user or a process with an effective uid equal to the
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.Va msg_perm.cuid
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or
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.Va msg_perm.uid
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values in the data structure associated with the queue can do this.
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.El
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.Pp
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The permission to read from or write to a message queue (see
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.Xr msgsnd 2
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and
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.Xr msgrcv 2 )
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is determined by the
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.Va msg_perm.mode
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field in the same way as is done with files (see
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.Xr chmod 2 ) ,
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but the effective uid can match either the
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.Va msg_perm.cuid
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field or the
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.Va msg_perm.uid
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field, and the
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effective gid can match either
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.Va msg_perm.cgid
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or
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.Va msg_perm.gid .
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.Sh RETURN VALUES
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Upon successful completion, a value of 0 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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.Fn msgctl
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EPERM
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.Fa cmd
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is equal to
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.Dv IPC_SET
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or
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.Dv IPC_RMID
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and the caller is not the super-user, nor does
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the effective uid match either the
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.Va msg_perm.uid
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or
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.Va msg_perm.cuid
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fields of the data structure associated with the message queue.
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.Pp
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An attempt was made to increase the value of
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.Va msg_qbytes
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through
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.Dv IPC_SET ,
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but the caller is not the super-user.
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.It Bq Er EACCES
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.Fa cmd
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is
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.Dv IPC_STAT
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and the caller has no read permission for this message queue.
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.It Bq Er EINVAL
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.Fa msqid
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is not a valid message queue identifier.
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.Pp
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.Fa cmd
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is not a valid command.
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.It Bq Er EFAULT
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.Fa buf
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specifies an invalid address.
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.El
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.Sh SEE ALSO
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.Xr msgget 2 ,
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.Xr msgrcv 2 ,
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.Xr msgsnd 2
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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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