illumos: manual page: semids.2

SEMIDS(2) System Calls SEMIDS(2)

NAME

semids - discover all semaphore identifiers

SYNOPSIS

#include <sys/sem.h>

int semids(int *buf, uint_t nids, uint_t *pnids);

DESCRIPTION

The semids() function copies all active semaphore 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 semaphore 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 semaphore 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 semaphore identifiers in
the system, buf is ignored.

RETURN VALUES

Upon successful completion, semids() returns 0. Otherwise, -1 is
returned and errno is set to indicate the error.

ERRORS

The semids() function will fail if:

EFAULT
The buf or pnids argument points to an illegal address.

USAGE

The semids() function returns a snapshot of all the active semaphore
identifiers in the system. More may be added and some may be removed
before they can be used by the caller.

EXAMPLES

Example 1 semids() example

This is sample C code indicating how to use the semids() function.

void
examine_semids()
{
int *ids = NULL;
uint_t nids = 0;
uint_t n;
int i;

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

free(ids);
}

ATTRIBUTES