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Added man pages for msgctl(3), msgget(3), msgrcv(3) and msgsnd(3).
Obtained from: NetBSD
This commit is contained in:
Mike Pritchard
parent
b156b34dfe
commit
2375385da1
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=14053
@ -46,7 +46,9 @@ MAN3+= gen/alarm.3 gen/clock.3 gen/confstr.3 gen/config_open.3 \
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gen/getmntinfo.3 gen/getnetgrent.3 gen/getpagesize.3 gen/getpass.3 \
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gen/getpwent.3 gen/getttyent.3 gen/getvfsent.3 gen/getusershell.3 \
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gen/glob.3 \
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gen/initgroups.3 gen/isinf.3 gen/ldexp.3 gen/modf.3 gen/nice.3 \
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gen/initgroups.3 gen/isinf.3 gen/ldexp.3 \
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gen/msgctl.3 gen/msgget.3 gen/msgrcv.3 gen/msgsnd.3 \
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gen/modf.3 gen/nice.3 \
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gen/nlist.3 gen/pause.3 gen/popen.3 gen/psignal.3 gen/pwcache.3 \
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gen/raise.3 gen/rand48.3 gen/scandir.3 gen/setjmp.3 gen/setmode.3 \
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gen/siginterrupt.3 gen/signal.3 gen/sigsetops.3 gen/sleep.3 \
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201
lib/libc/gen/msgctl.3
Normal file
201
lib/libc/gen/msgctl.3
Normal file
@ -0,0 +1,201 @@
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.\" $NetBSD: msgctl.2,v 1.1 1995/10/16 23:49:15 jtc 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
|
||||
.\" are met:
|
||||
.\" 1. Redistributions of source code must retain the above copyright
|
||||
.\" notice, this list of conditions and the following disclaimer.
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||||
.\" 2. Redistributions in binary form must reproduce the above copyright
|
||||
.\" 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
|
||||
.\" 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
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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 17, 1995
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.Dt MSGCTL 3
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.Os NetBSD
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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 SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/ipc.h>
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.Fd #include <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 some control operations on the message queue specified
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by
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.Fa msqid .
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Each message queue has a data structure associated with it, parts of which
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may be altered by
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.Fn msgctl
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and parts of which determine the actions of
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.Fn msgctl .
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The data structure is defined in
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.Aq Pa sys/msg.h
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and contains (amongst others) the following members:
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.Bd -literal
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struct msqid_ds {
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struct ipc_perm msg_perm; /* msg queue permission bits */
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u_long msg_cbytes; /* # of bytes in use on the queue */
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u_long msg_qnum; /* # of msgs in the queue */
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u_long 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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};
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.Ed
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The
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.Bf -literal
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ipc_perm
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.Ef
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structure used inside the
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.Bf -literal
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shmid_ds
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.Ef
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structure is defined in
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.Aq Pa sys/ipc.h
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and looks like this:
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.Bd -literal
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struct ipc_perm {
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ushort cuid; /* creator user id */
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ushort cgid; /* creator group id */
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ushort uid; /* user id */
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ushort gid; /* group id */
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ushort mode; /* permission (9 bits, see chmod(2)) */
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ushort seq; /* sequence # (to generate unique id) */
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key_t key; /* user specified msg/sem/shm key */
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};
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.Ed
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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. Values for
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.Va msg_qbytes
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that exceed the system limit (MSGMNB from
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.Aq Pa 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. Only the super-user or a process
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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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The permission to read from or write to a message queue (see
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.Xr msgsnd 3
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and
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.Xr msgrcv 3 )
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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
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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. Otherwise, -1 is
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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 IPC_SET or IPC_RMID 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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An attempt is made to increase the value of
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.Va msg_qbytes
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through IPC_SET
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but the caller is not the super-user.
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.It Bq Er EACCESS
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The command is 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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.Va 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 msgsnd 3 ,
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.Xr msgrcv 3 ,
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.Xr msgget 3
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.Sh HISTORY
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Message queues appeared in the first release of AT&T Unix System V.
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126
lib/libc/gen/msgget.3
Normal file
126
lib/libc/gen/msgget.3
Normal file
@ -0,0 +1,126 @@
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.\" $NetBSD: msgget.2,v 1.1 1995/10/16 23:49:19 jtc 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
|
||||
.\" 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.
|
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.\"/
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.Dd August 17, 1995
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.Dt MSGGET 3
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.Os NetBSD
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.Sh NAME
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.Nm msgget
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.Nd get message queue
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/ipc.h>
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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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.Fn msgget
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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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A message queue is created if either
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.Fa key
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is equal to IPC_PRIVATE, or
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.Fa key
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does not have a message queue identifier associated with it, and the IPC_CREAT
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bit is set in
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.Fa msgflg.
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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 3 )
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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_cbytes ,
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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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(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 EACESS
|
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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 IPC_CREAT and IPC_EXCL 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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IPC_CREAT was 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 3 ,
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.Xr msgrcv 3 ,
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.Xr msgsnd 3
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.Sh HISTORY
|
||||
Message queues appeared in the first release of AT&T Unix System V.
|
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181
lib/libc/gen/msgrcv.3
Normal file
181
lib/libc/gen/msgrcv.3
Normal file
@ -0,0 +1,181 @@
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.\" $NetBSD: msgrcv.2,v 1.1 1995/10/16 23:49:20 jtc Exp $
|
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.\"
|
||||
.\" 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 August 17, 1995
|
||||
.Dt MSGRCV 3
|
||||
.Os NetBSD
|
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.Sh NAME
|
||||
.Nm msgrcv
|
||||
.Nd receive a message from a message queue
|
||||
.Sh SYNOPSIS
|
||||
.Fd #include <sys/types.h>
|
||||
.Fd #include <sys/ipc.h>
|
||||
.Fd #include <sys/msg.h>
|
||||
.Ft int
|
||||
.Fn msgrcv "int msqid" "void *msgp" "size_t msgsz" "long msgtyp" "int msgflg"
|
||||
.Sh DESCRIPTION
|
||||
The
|
||||
.Fn msgrcv
|
||||
function receives a message from the message queue specified in
|
||||
.Fa msqid ,
|
||||
and places it into the structure pointed to by
|
||||
.Fa msgp .
|
||||
This structure should consist of the following members:
|
||||
.Bd -literal
|
||||
long mtype; /* message type */
|
||||
char mtext[1]; /* body of message */
|
||||
.Ed
|
||||
|
||||
.Va mtype
|
||||
is an integer greater than 0 that can be used for selecting messages,
|
||||
.Va mtext
|
||||
is an array of bytes, with a size up to that of the system limit (MSGMAX).
|
||||
|
||||
The value of
|
||||
.Fa msgtyp
|
||||
has one of the following meanings:
|
||||
.Bl -bullet
|
||||
.It
|
||||
.Fa msgtyp
|
||||
is greater than 0. The first message of type
|
||||
.Fa msgtyp
|
||||
will be received.
|
||||
.It
|
||||
.Fa msgtyp
|
||||
is equal to 0. The first message on the queue will be received.
|
||||
.It
|
||||
.Fa msgtyp
|
||||
is less than 0. The first message of the lowest message type that is
|
||||
less than or equal to the absolute value of
|
||||
.Fa msgtyp
|
||||
will be received.
|
||||
.El
|
||||
|
||||
.Fa msgsz
|
||||
specifies the maximum length of the requested message. If the received
|
||||
message has a length greater than
|
||||
.Fa msgsz
|
||||
it will be silently truncated if the MSG_NOERROR flag is set in
|
||||
.Fa msgflg ,
|
||||
otherwise an error will be returned.
|
||||
|
||||
If no matching message is present on the message queue specified by
|
||||
.Fa msqid ,
|
||||
the behavior of
|
||||
.Fn msgrcv
|
||||
depends on whether the IPC_NOWAIT flag is set in
|
||||
.Fa msgflg
|
||||
or not. If IPC_NOWAIT is set,
|
||||
.Fn msgrcv
|
||||
will immediately return a value of -1, and set
|
||||
.Va errno
|
||||
to EAGAIN. If IPC_NOWAIT is not set, the calling process will be blocked
|
||||
until:
|
||||
.Bl -bullet
|
||||
.It
|
||||
A message of the requested type becomes available on the message queue.
|
||||
.It
|
||||
The message queue is removed, in which case -1 will be returned, and
|
||||
.Va errno
|
||||
set to EINVAL.
|
||||
.It
|
||||
A signal is received and caught. -1 is returned, and
|
||||
.Va errno
|
||||
set to EINTR.
|
||||
.El
|
||||
|
||||
If a message is successfully received, the data structure associated with
|
||||
.Fa msqid
|
||||
is updated as follows:
|
||||
.Bl -bullet
|
||||
.It
|
||||
.Va msg_cbytes
|
||||
is decremented by the size of the message.
|
||||
.It
|
||||
.Va msg_lrpid
|
||||
is set to the pid of the caller.
|
||||
.It
|
||||
.Va msg_lrtime
|
||||
is set to the current time.
|
||||
.It
|
||||
.Va msg_qnum
|
||||
is decremented by 1.
|
||||
.Sh RETURN VALUES
|
||||
Upon successful completion,
|
||||
.Fn msgrcv
|
||||
returns the number of bytes received into the
|
||||
.Va mtext
|
||||
field of the structure pointed to by
|
||||
.Fa msgp .
|
||||
Otherwise, -1 is returned, and
|
||||
.Va errno
|
||||
set to indicate the error.
|
||||
.Sh ERRORS
|
||||
.Fn msgrcv
|
||||
will fail if:
|
||||
.Bl -tag -width Er
|
||||
.It Bq Er EINVAL
|
||||
.Fa msqid
|
||||
is not a valid message queue identifier
|
||||
|
||||
The message queue was removed while
|
||||
.Fn msgrcv
|
||||
was waiting for a message of the requested type to become available on it.
|
||||
|
||||
.Fa msgsz
|
||||
is less than 0.
|
||||
.It Bq Er E2BIG
|
||||
A matching message was received, but its size was greater than
|
||||
.Fa msgsz
|
||||
and the MSG_NOERROR flag was not set in
|
||||
.Fa msgflg .
|
||||
.It Bq Er EACCESS
|
||||
The calling process does not have read access to the message queue.
|
||||
.It Bq Er EFAULT
|
||||
.Fa msgp
|
||||
points to an invalid address.
|
||||
.It Bq Er EINTR
|
||||
The system call was interrupted by the delivery of a signal.
|
||||
.It Bq Er EAGAIN
|
||||
There is no message of the requested type available on the message queue,
|
||||
and IPC_NOWAIT is set in
|
||||
.Fa msgflg .
|
||||
.Sh SEE ALSO
|
||||
.Xr msgsnd 3 ,
|
||||
.Xr msgctl 3 ,
|
||||
.Xr msgget 3
|
||||
.Sh BUGS
|
||||
NetBSD and FreeBSD do not define the EIDRM error value, which should be used in
|
||||
the case of a removed message queue, nor the ENOMSG value, which
|
||||
should be used when no suitable message is available and IPC_NOWAIT
|
||||
is set.
|
||||
.Sh HISTORY
|
||||
Message queues appeared in the first release of AT&T Unix System V.
|
||||
145
lib/libc/gen/msgsnd.3
Normal file
145
lib/libc/gen/msgsnd.3
Normal file
@ -0,0 +1,145 @@
|
||||
.\" $NetBSD: msgsnd.2,v 1.1 1995/10/16 23:49:24 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.
|
||||
.\"/
|
||||
.Dd August 17, 1995
|
||||
.Dt MSGSND 3
|
||||
.Os NetBSD
|
||||
.Sh NAME
|
||||
.Nm msgsnd
|
||||
.Nd send a message to a message queue
|
||||
.Sh SYNOPSIS
|
||||
.Fd #include <sys/types.h>
|
||||
.Fd #include <sys/ipc.h>
|
||||
.Fd #include <sys/msg.h>
|
||||
.Ft int
|
||||
.Fn msgsnd "int msqid" "void *msgp" "size_t msgsz" "int msgflg"
|
||||
.Sh DESCRIPTION
|
||||
The
|
||||
.Fn msgsnd
|
||||
function sends a message from the message queue specified in
|
||||
.Fa msqid .
|
||||
.Fa msgp
|
||||
points to a structure containing the message. This structure should
|
||||
consist of the following members:
|
||||
.Bd -literal
|
||||
long mtype; /* message type */
|
||||
char mtext[1]; /* body of message */
|
||||
.Ed
|
||||
|
||||
.Va mtype
|
||||
is an integer greater than 0 that can be used for selecting messages (see
|
||||
.Xr msgrcv 3 ) ,
|
||||
.Va mtext
|
||||
is an array of bytes, with a size up to that of the system limit (MSGMAX).
|
||||
|
||||
If the number of bytes already on the message queue plus
|
||||
.Fa msgsz
|
||||
is bigger than the maximum number of bytes on the message queue (
|
||||
.Va msg_qbytes ,
|
||||
see
|
||||
.Xr msgctl 3 ) ,
|
||||
or the number of messages on all queues system-wide is already equal to
|
||||
the system limit,
|
||||
.Fa msgflg
|
||||
determines the action of
|
||||
.Fn msgsnd .
|
||||
If
|
||||
.Fa msgflg
|
||||
has IPC_NOWAIT mask set in it, the call will return immediately. If
|
||||
.Fa msgflg
|
||||
does not have IPC_NOWAIT set in it, the call will block until:
|
||||
.Bl -bullet
|
||||
.It
|
||||
The condition which caused the call to block does no longer exist.
|
||||
The message will be sent.
|
||||
.It
|
||||
The message queue is removed, in which case -1 will be returned, and
|
||||
.Va errno
|
||||
is set to EINVAL.
|
||||
.It
|
||||
The caller catches a signal. The call returns with
|
||||
.Va errno
|
||||
set to EINTR.
|
||||
.El
|
||||
|
||||
After a successful call, the data structure associated with the message
|
||||
queue is updated in the following way:
|
||||
.Bl -bullet
|
||||
.It
|
||||
.Va msg_cbytes
|
||||
is incremented by the size of the message.
|
||||
.It
|
||||
.Va msg_qnum
|
||||
is incremented by 1.
|
||||
.It
|
||||
.Va msg_lspid
|
||||
is set to the pid of the calling process.
|
||||
.It
|
||||
.Va msg_stime
|
||||
is set to the current time.
|
||||
.El
|
||||
.Sh RETURN VALUES
|
||||
Upon successful completion, 0 is returned. Otherwise, -1 is returned and
|
||||
.Va errno
|
||||
is set to indicate the error.
|
||||
.Sh ERRORS
|
||||
.Fn msgsnd
|
||||
will fail if:
|
||||
.Bl -tag -width Er
|
||||
.It Bq Er EINVAL
|
||||
.Fa msqid
|
||||
is not a valid message queue identifier
|
||||
|
||||
The message queue was removed while
|
||||
.Fn msgsnd
|
||||
was waiting for a resource to become available in order to deliver the
|
||||
message.
|
||||
|
||||
.Fa msgsz
|
||||
is less than 0, or greater than
|
||||
.Va msg_qbytes .
|
||||
.It Bq Er EACCESS
|
||||
The calling process does not have write access to the message queue.
|
||||
.It Bq Er EAGAIN
|
||||
There was no space for this message either on the queue, or in the whole
|
||||
system, and IPC_NOWAIT was set in
|
||||
.Fa msgflg .
|
||||
.It Bq Er EFAULT
|
||||
.Fa msgp
|
||||
points to an invalid address.
|
||||
.It Bq Er EINTR
|
||||
The system call was interrupted by the delivery of a signal.
|
||||
.El
|
||||
.Sh BUGS
|
||||
NetBSD and FreeBSD do not define the EIDRM error value, which should be used
|
||||
in the case of a removed message queue.
|
||||
.Sh HISTORY
|
||||
Message queues appeared in the first release of AT&T Unix System V.
|
||||
Loading…
Reference in New Issue
Block a user