src/ipc/semstat.c

   1 /*****************************************************************************
   2  Excerpt from "Linux Programmer's Guide - Chapter 6"
   3  (C)opyright 1994-1995, Scott Burkett
   4  *****************************************************************************
   5  MODULE: semstat.c
   6  *****************************************************************************
   7  A companion command line tool for the semtool package.  semstat displays
   8  the current value of all semaphores in the set created by semtool.
   9  *****************************************************************************/
  10 /*
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  24  *
  25  * See the COPYING file for license information.
  26  */
  27
  28 #if HAVE_CONFIG_H
  29 #  include "config.h"
  30 #endif
  31
  32 #include "common.h"
  33
  34 #if HAVE_SYS_IPC_H
  35 #  include <sys/ipc.h>
  36 #endif
  37 #if HAVE_SYS_SEM_H
  38 #  include <sys/sem.h>
  39 #endif
  40
  41 /* arg for semctl system calls. */
  42 union semun {
  43   int val;                      /* value for SETVAL */
  44   struct semid_ds *buf;         /* buffer for IPC_STAT & IPC_SET */
  45   ushort *array;                /* array for GETALL & SETALL */
  46   struct seminfo *__buf;        /* buffer for IPC_INFO */
  47   void *__pad;
  48 };
  49
  50 int get_sem_count(int sid);
  51 void show_sem_usage(int sid);
  52 int get_sem_count(int sid);
  53 void dispval(int sid);
  54
  55 int main(int argc, char *argv[])
  56 {
  57         key_t key;
  58         int   semset_id;
  59
  60         /* Create unique key via call to ftok() */
  61         key = ftok(".", 's');
  62
  63         /* Open the semaphore set - do not create! */
  64         if((semset_id = semget(key, 1, 0666)) == -1)
  65         {
  66                 printf("Semaphore set does not exist\n");
  67                 exit(1);
  68         }
  69
  70         show_sem_usage(semset_id);
  71         return(0);
  72 }
  73
  74 void show_sem_usage(int sid)
  75 {
  76         int cntr=0, maxsems, semval;
  77
  78         maxsems = get_sem_count(sid);
  79
  80         while(cntr < maxsems) {
  81                 semval = semctl(sid, cntr, GETVAL, 0);
  82                 printf("Semaphore #%d:  --> %d\n", cntr, semval);
  83                 cntr++;
  84         }
  85 }
  86
  87 int get_sem_count(int sid)
  88 {
  89         int rc;
  90         struct semid_ds mysemds;
  91         union semun semopts;
  92
  93         /* Get current values for internal data structure */
  94         semopts.buf = &mysemds;
  95
  96         if((rc = semctl(sid, 0, IPC_STAT, semopts)) == -1) {
  97                 perror("semctl");
  98                 exit(1);
  99         }
 100
 101         /* return number of semaphores in set */
 102         return(semopts.buf->sem_nsems);
 103 }
 104
 105 void dispval(int sid)
 106 {
 107         int semval;
 108
 109         semval = semctl(sid, 0, GETVAL, 0);
 110         printf("semval is %d\n", semval);
 111 }