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': writeshm(shmid, segptr, argv[2]);
  82                           break;
  83                 case 'r': readshm(shmid, segptr);
  84                           break;
  85                 case 'd': removeshm(shmid);
  86                           break;
  87                 case 'm': changemode(shmid, argv[2]);
  88                           break;
  89                  default: usage();
  90
  91         }
  92 }
  93
  94 writeshm(int shmid, char *segptr, char *text)
  95 {
  96         strcpy(segptr, text);
  97         printf("Done...\n");
  98 }
  99
 100 readshm(int shmid, char *segptr)
 101 {
 102         printf("segptr: %s\n", segptr);
 103 }
 104
 105 removeshm(int shmid)
 106 {
 107         shmctl(shmid, IPC_RMID, 0);
 108         printf("Shared memory segment marked for deletion\n");
 109 }
 110
 111 changemode(int shmid, char *mode)
 112 {
 113         struct shmid_ds myshmds;
 114
 115         /* Get current values for internal data structure */
 116         shmctl(shmid, IPC_STAT, &myshmds);
 117
 118         /* Display old permissions */
 119         printf("Old permissions were: %o\n", myshmds.shm_perm.mode);
 120
 121         /* Convert and load the mode */
 122         sscanf(mode, "%o", &myshmds.shm_perm.mode);
 123
 124         /* Update the mode */
 125         shmctl(shmid, IPC_SET, &myshmds);
 126
 127         printf("New permissions are : %o\n", myshmds.shm_perm.mode);
 128 }
 129
 130 usage()
 131 {
 132         fprintf(stderr, "shmtool - A utility for tinkering with shared memory\n");
 133         fprintf(stderr, "\nUSAGE:  shmtool (w)rite <text>\n");
 134         fprintf(stderr, "                (r)ead\n");
 135         fprintf(stderr, "                (d)elete\n");
 136         fprintf(stderr, "                (m)ode change <octal mode>\n");
 137         exit(1);
 138 }
 139