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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 inte-
       gers the buffer can contain, as specified by nids.  If the size of  the
       buffer is insufficient to contain all of the active message queue iden-
       tifiers 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  identi-
       fiers 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(5) for descriptions of the following attributes:


       tab()     allbox;     cw(2.750000i)|    cw(2.750000i)    lw(2.750000i)|
       lw(2.750000i).  ATTRIBUTE TYPEATTRIBUTE VALUE MT-LevelAsync-Signal-Safe


SEE ALSO
       ipcrm(1),  ipcs(1),   intro(2),   msgctl(2),   msgget(2),   msgsnap(2),
       msgrcv(2), msgsnd(2), attributes(5)



SunOS 5.10                        8 Mar 2000                         msgids(2)