'\" te
.\" Copyright (c) 2000, Sun Microsystems, Inc.
.\" All Rights Reserved.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
.TH MSGIDS 2 "Mar 8, 2000"
.SH NAME
msgids \- discover all message queue identifiers
.SH SYNOPSIS
.LP
.nf
#include <sys/msg.h>

\fBint\fR \fBmsgids\fR(\fBint *\fR\fIbuf\fR, \fBuint_t\fR \fInids\fR, \fBuint_t  *\fR\fIpnids\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBmsgids()\fR function copies all active message queue identifiers from
the system into the user-defined buffer specified by \fIbuf\fR, provided that
the number of such identifiers is not greater than the number of integers the
buffer can contain, as specified by \fInids\fR.  If the size of the buffer is
insufficient to contain all of the active message queue identifiers in the
system, none are copied.
.sp
.LP
Whether or not the size of the buffer is sufficient to contain all of them, the
number of active message queue identifiers in the system is copied into the
unsigned integer pointed to by \fIpnids\fR.
.sp
.LP
If \fInids\fR is 0 or less than the number of active message queue identifiers
in the system, \fIbuf\fR is ignored.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBmsgids()\fR returns \fB0\fR.  Otherwise,
\fB\(mi1\fR is returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBmsgids()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEFAULT\fR\fR
.ad
.RS 10n
The \fIbuf\fR or \fIpnids\fR argument points to an illegal address.
.RE

.SH USAGE
.sp
.LP
The \fBmsgids()\fR function returns a snapshot of all the active message queue
identifiers in the system.  More may be added and some may be removed before
they can be used by the caller.
.SH EXAMPLES
.LP
\fBExample 1 \fR\fBmsgids()\fR example
.sp
.LP
This is sample C code indicating how to use the \fBmsgids()\fR function (see
\fBmsgsnap\fR(2)):

.sp
.in +2
.nf
void
examine_queues()
{
     int *ids = NULL;
     uint_t nids = 0;
     uint_t n;
     int i;

     for (;;) {
          if (msgids(ids, nids, &n) != 0) {
               perror("msgids");
               exit(1);
          }
          if (n <= nids)     /* we got them all */
               break;
          /* we need a bigger buffer */
          ids = realloc(ids, (nids = n) * sizeof (int));
     }

     for (i = 0; i < n; i++)
          process_msgid(ids[i]);

     free(ids);
}
.fi
.in -2

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT-Level	Async-Signal-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR ipcrm (1),
.BR ipcs (1),
.BR Intro (2),
.BR msgctl (2),
.BR msgget (2),
.BR msgrcv (2),
.BR msgsnap (2),
.BR msgsnd (2),
.BR attributes (7)