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 modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation, either version 3 of the License, or
  14  * (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, see <http://www.gnu.org/licenses/>.
  23  *
  24  * See the COPYING file for full license information.
  25  */
  26
  27 #if HAVE_CONFIG_H
  28 # include "config.h"
  29 #endif
  30
  31 #include "common.h"
  32
  33 #if HAVE_SYS_IPC_H
  34 # include <sys/ipc.h>
  35 #endif
  36 #if HAVE_SYS_SHM_H
  37 # include <sys/shm.h>
  38 #endif
  39
  40 #define SEGSIZE 100
  41
  42 int
  43 usage ()
  44 {
  45   fprintf (stderr, "shmtool - A utility for tinkering with shared memory\n");
  46   fprintf (stderr, "\nUSAGE:  shmtool (w)rite <text>\n");
  47   fprintf (stderr, "                (r)ead\n");
  48   fprintf (stderr, "                (d)elete\n");
  49   fprintf (stderr, "                (m)ode change <octal mode>\n");
  50   exit (1);
  51 }
  52
  53 int
  54 writeshm (int shmid, char *segptr, char *text)
  55 {
  56   strcpy (segptr, text);
  57   printf ("Done...\n");
  58 }
  59
  60 int
  61 readshm (int shmid, char *segptr)
  62 {
  63   printf ("segptr: %s\n", segptr);
  64 }
  65
  66 int
  67 removeshm (int shmid)
  68 {
  69   shmctl (shmid, IPC_RMID, 0);
  70   printf ("Shared memory segment marked for deletion\n");
  71 }
  72
  73 int
  74 changemode (int shmid, char *mode)
  75 {
  76   struct shmid_ds myshmds;
  77
  78   /* Get current values for internal data structure */
  79   shmctl (shmid, IPC_STAT, &myshmds);
  80
  81   /* Display old permissions */
  82   printf ("Old permissions were: %o\n", myshmds.shm_perm.mode);
  83
  84   /* Convert and load the mode */
  85   sscanf (mode, "%o", &myshmds.shm_perm.mode);
  86
  87   /* Update the mode */
  88   shmctl (shmid, IPC_SET, &myshmds);
  89
  90   printf ("New permissions are : %o\n", myshmds.shm_perm.mode);
  91 }
  92
  93 int
  94 main (int argc, char *argv[])
  95 {
  96   key_t key;
  97   int shmid, cntr;
  98   char *segptr;
  99
 100   if (argc == 1)
 101     usage ();
 102
 103   /* Create unique key via call to ftok() */
 104   key = ftok (".", 'S');
 105
 106   /* Open the shared memory segment - create if necessary */
 107   if ((shmid = shmget (key, SEGSIZE, IPC_CREAT | IPC_EXCL | 0666)) == -1)
 108     {
 109       printf ("Shared memory segment exists - opening as client\n");
 110
 111       /* Segment probably already exists - try as a client */
 112       if ((shmid = shmget (key, SEGSIZE, 0)) == -1)
 113         {
 114           perror ("shmget");
 115           exit (1);
 116         }
 117     }
 118   else
 119     {
 120       printf ("Creating new shared memory segment\n");
 121     }
 122
 123   /* Attach (map) the shared memory segment into the current process */
 124   if ((segptr = shmat (shmid, 0, 0)) == ((char *) -1))
 125     {
 126       perror ("shmat");
 127       exit (1);
 128     }
 129
 130   switch (tolower (argv[1][0]))
 131     {
 132     case 'w':
 133       writeshm (shmid, segptr, argv[2]);
 134       break;
 135     case 'r':
 136       readshm (shmid, segptr);
 137       break;
 138     case 'd':
 139       removeshm (shmid);
 140       break;
 141     case 'm':
 142       changemode (shmid, argv[2]);
 143       break;
 144     default:
 145       usage ();
 146
 147     }
 148 }