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 {
  44   int val;                      /* value for SETVAL */
  45   struct semid_ds *buf;         /* buffer for IPC_STAT & IPC_SET */
  46   ushort *array;                /* array for GETALL & SETALL */
  47   struct seminfo *__buf;        /* buffer for IPC_INFO */
  48   void *__pad;
  49 };
  50
  51 int get_sem_count (int sid);
  52 void show_sem_usage (int sid);
  53 int get_sem_count (int sid);
  54 void dispval (int sid);
  55
  56 int
  57 main (int argc, char *argv[])
  58 {
  59   key_t key;
  60   int semset_id;
  61
  62   /* Create unique key via call to ftok() */
  63   key = ftok (".", 's');
  64
  65   /* Open the semaphore set - do not create! */
  66   if ((semset_id = semget (key, 1, 0666)) == -1)
  67     {
  68       printf ("Semaphore set does not exist\n");
  69       exit (1);
  70     }
  71
  72   show_sem_usage (semset_id);
  73   return (0);
  74 }
  75
  76 void
  77 show_sem_usage (int sid)
  78 {
  79   int cntr = 0, maxsems, semval;
  80
  81   maxsems = get_sem_count (sid);
  82
  83   while (cntr < maxsems)
  84     {
  85       semval = semctl (sid, cntr, GETVAL, 0);
  86       printf ("Semaphore #%d:  --> %d\n", cntr, semval);
  87       cntr++;
  88     }
  89 }
  90
  91 int
  92 get_sem_count (int sid)
  93 {
  94   int rc;
  95   struct semid_ds mysemds;
  96   union semun semopts;
  97
  98   /* Get current values for internal data structure */
  99   semopts.buf = &mysemds;
 100
 101   if ((rc = semctl (sid, 0, IPC_STAT, semopts)) == -1)
 102     {
 103       perror ("semctl");
 104       exit (1);
 105     }
 106
 107   /* return number of semaphores in set */
 108   return (semopts.buf->sem_nsems);
 109 }
 110
 111 void
 112 dispval (int sid)
 113 {
 114   int semval;
 115
 116   semval = semctl (sid, 0, GETVAL, 0);
 117   printf ("semval is %d\n", semval);
 118 }