'\" te
.\" Copyright (c) 2000, Sun Microsystems, Inc. All Rights Reserved.
.TH shmids 2 "8 Mar 2000" "SunOS 5.11" "System Calls"
.SH NAME
shmids \- discover all shared memory identifiers
.SH SYNOPSIS
.LP
.nf
#include <sys/shm.h>

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

.SH DESCRIPTION
.sp
.LP
The \fBshmids()\fR function copies all active shared memory 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 shared memory 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 shared memory 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 shared memory identifiers in the system, \fIbuf\fR is ignored.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBshmids()\fR returns \fB0\fR.  Otherwise, \fB\(mi1\fR is returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBshmids()\fR function will fail if:
.sp
.ne 2
.mk
.na
\fB\fBEFAULT\fR\fR
.ad
.RS 10n
.rt  
The \fIbuf\fR or \fIpnids\fR argument points to an illegal address.
.RE

.SH USAGE
.sp
.LP
The \fBshmids()\fR function returns a snapshot of all the active shared memory 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\fBshmids()\fR example
.sp
.LP
This is sample C code indicating how to use the \fBshmids()\fR function.

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

     for (;;) {
          if (shmids(ids, nids, &n) != 0) {
               perror("shmids");
               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_shmid(ids[i]);

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

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
MT-LevelAsync-Signal-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBipcrm\fR(1), \fBipcs\fR(1), \fBIntro\fR(2), \fBshmctl\fR(2), \fBshmget\fR(2), \fBshmop\fR(2), \fBattributes\fR(5)