146 lines
4.6 KiB
Groff
146 lines
4.6 KiB
Groff
.\" $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.
|