src/ipc/shmtool.c

   1 /*****************************************************************************
   2  Excerpt from "Linux Programmer's Guide - Chapter 6"
   3  (C)opyright 1994-1995, Scott Burkett
   4  *****************************************************************************
   5  MODULE: shmtool.c
   6  *****************************************************************************
   7  A command line tool for tinkering with shared memory
   8
   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_SHM_H
  38 # include <sys/shm.h>
  39 #endif
  40
  41 #define SEGSIZE 100
  42
  43 main (int argc, char *argv[])
  44 {
  45   key_t key;
  46   int shmid, cntr;
  47   char *segptr;
  48
  49   if (argc == 1)
  50     usage ();
  51
  52   /* Create unique key via call to ftok() */
  53   key = ftok (".", 'S');
  54
  55   /* Open the shared memory segment - create if necessary */
  56   if ((shmid = shmget (key, SEGSIZE, IPC_CREAT | IPC_EXCL | 0666)) == -1)
  57     {
  58       printf ("Shared memory segment exists - opening as client\n");
  59
  60       /* Segment probably already exists - try as a client */
  61       if ((shmid = shmget (key, SEGSIZE, 0)) == -1)
  62         {
  63           perror ("shmget");
  64           exit (1);
  65         }
  66     }
  67   else
  68     {
  69       printf ("Creating new shared memory segment\n");
  70     }
  71
  72   /* Attach (map) the shared memory segment into the current process */
  73   if ((segptr = shmat (shmid, 0, 0)) == ((char *) -1))
  74     {
  75       perror ("shmat");
  76       exit (1);
  77     }
  78
  79   switch (tolower (argv[1][0]))
  80     {
  81     case 'w':
  82       writeshm (shmid, segptr, argv[2]);
  83       break;
  84     case 'r':
  85       readshm (shmid, segptr);
  86       break;
  87     case 'd':
  88       removeshm (shmid);
  89       break;
  90     case 'm':
  91       changemode (shmid, argv[2]);
  92       break;
  93     default:
  94       usage ();
  95
  96     }
  97 }
  98
  99 writeshm (int shmid, char *segptr, char *text)
 100 {
 101   strcpy (segptr, text);
 102   printf ("Done...\n");
 103 }
 104
 105 readshm (int shmid, char *segptr)
 106 {
 107   printf ("segptr: %s\n", segptr);
 108 }
 109
 110 removeshm (int shmid)
 111 {
 112   shmctl (shmid, IPC_RMID, 0);
 113   printf ("Shared memory segment marked for deletion\n");
 114 }
 115
 116 changemode (int shmid, char *mode)
 117 {
 118   struct shmid_ds myshmds;
 119
 120   /* Get current values for internal data structure */
 121   shmctl (shmid, IPC_STAT, &myshmds);
 122
 123   /* Display old permissions */
 124   printf ("Old permissions were: %o\n", myshmds.shm_perm.mode);
 125
 126   /* Convert and load the mode */
 127   sscanf (mode, "%o", &myshmds.shm_perm.mode);
 128
 129   /* Update the mode */
 130   shmctl (shmid, IPC_SET, &myshmds);
 131
 132   printf ("New permissions are : %o\n", myshmds.shm_perm.mode);
 133 }
 134
 135 usage ()
 136 {
 137   fprintf (stderr, "shmtool - A utility for tinkering with shared memory\n");
 138   fprintf (stderr, "\nUSAGE:  shmtool (w)rite <text>\n");
 139   fprintf (stderr, "                (r)ead\n");
 140   fprintf (stderr, "                (d)elete\n");
 141   fprintf (stderr, "                (m)ode change <octal mode>\n");
 142   exit (1);
 143 }