svsem/svsem_setall.c

+/* svsem_setall.c
+
+   Usage: svsem_setall semid value...
+
+   Set the values of all of the members of a System V semaphore set according
+   to the values supplied on the command line.
+*/
 #include <sys/types.h>
 #include <sys/sem.h>
 #include "semun.h"                      /* Definition of semun union */
 #include "tlpi_hdr.h"
 
 int
 main(int argc, char *argv[])
 {
     struct semid_ds ds;
     union semun arg;                    /* Fourth argument for semctl() */
     int j, semid;
 
     if (argc < 3 || strcmp(argv[1], "--help") == 0)
         usageErr("%s semid val...\n", argv[0]);
 
     semid = getInt(argv[1], 0, "semid");
 
     /* Obtain size of semaphore set */
 
     arg.buf = &ds;
     if (semctl(semid, 0, IPC_STAT, arg) == -1)
         errExit("semctl");
 
+    /* The number of values supplied on the command line must match the
+       number of semaphores in the set */
+
     if (ds.sem_nsems != argc - 2)
         cmdLineErr("Set contains %ld semaphores, but %d values were supplied\n",
                 (long) ds.sem_nsems, argc - 2);
 
     /* Set up array of values; perform semaphore initialization */
 
     arg.array = calloc(ds.sem_nsems, sizeof(arg.array[0]));
     if (arg.array == NULL)
         errExit("calloc");
 
     for (j = 2; j < argc; j++)
         arg.array[j - 2] = getInt(argv[j], 0, "val");
 
     if (semctl(semid, 0, SETALL, arg) == -1)
         errExit("semctl-SETALL");
     printf("Semaphore values changed (PID=%ld)\n", (long) getpid());
 
     exit(EXIT_SUCCESS);
 }