List all the Value-Action Pairs for a Specific Resource Control

The following example lists all the value-action pairs for a specific resource control, task.max-lwps. The key point for the example is that getrctl(2) takes two resource control blocks, and returns the resource control block for the RCTL_NEXT flag. To iterate through all resource control blocks, repeatedly swap the resource control block values, as shown here using the rcb_tmp rctl block.

rctlblk_t *rcb1, *rcb2, *rcb_tmp;
	...
/* Omit return value checking/error processing to keep code sample short */
rcb1 = calloc(1, rctlblk_size()); /* rctl blocks are opaque: */
                               /* "rctlblk_t rcb" does not work */
rcb2 = calloc(1, rctlblk_size());
getrctl("task.max-lwps", NULL, rcb1, RCTL_FIRST);
while (1) {
     print_rctl(rcb1);
     rcb_tmp = rcb2;
     rcb2 = rcb1;
     rcb1 = rcb_tmp;        /* swap rcb1 with rcb2 */
     if (getrctl("task.max-lwps", rcb2,  rcb1, RCTL_NEXT) == -1) {
          if (errno == ENOENT) {
               break;
     } else {
          perror("getrctl");
          exit (1);
     }
     }
}