MSGIDS(2) System Calls MSGIDS(2)
NAME
msgids - discover all message queue identifiers
SYNOPSIS
#include <sys/msg.h>
int msgids(
int *buf,
uint_t nids,
uint_t *pnids);
DESCRIPTION
The
msgids() function copies all active message queue identifiers from
the system into the user-defined buffer specified by
buf, provided that
the number of such identifiers is not greater than the number of integers
the buffer can contain, as specified by
nids. If the size of the buffer
is insufficient to contain all of the active message queue identifiers in
the system, none are copied.
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
pnids.
If
nids is 0 or less than the number of active message queue identifiers
in the system,
buf is ignored.
RETURN VALUES
Upon successful completion,
msgids() returns
0. Otherwise,
-1 is
returned and
errno is set to indicate the error.
ERRORS
The
msgids() function will fail if:
EFAULT The
buf or
pnids argument points to an illegal address.
USAGE
The
msgids() 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.
EXAMPLES
Example 1 msgids() example
This is sample C code indicating how to use the
msgids() function (see
msgsnap(2)):
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);
}
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+---------------+-------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-------------------+
|MT-Level | Async-Signal-Safe |
+---------------+-------------------+
SEE ALSO
ipcrm(1),
ipcs(1),
Intro(2),
msgctl(2),
msgget(2),
msgrcv(2),
msgsnap(2),
msgsnd(2),
attributes(7) March 8, 2000
MSGIDS(2)