shared_memory.cpp

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

#define SHM_SIZE 1024  /* make it a 1K shared memory segment */

key_t key;
int shmid;
char *data;
int mode;

void attach_memory(){
  /* make the key: */
  if ((key = ftok("/tmp/chess_shared_memory.txt", 'R')) == -1) /*Here the file must exist */ 
  {
    perror("ftok");
    exit(1);
  }

  /*  create the segment: */
  if ((shmid = shmget(key, SHM_SIZE, 0644 | IPC_CREAT)) == -1) {
    perror("shmget");
    exit(1);
  }

  /* attach to the segment to get a pointer to it: */
  data = (char*)shmat(shmid, (void *)0, 0);
  if (data == (char *)(-1)) {
    perror("shmat");
    exit(1);
  }

  ///* read or modify the segment, based on the command line: */
  //if (argc == 2) {
  //  printf("writing to segment: \"%s\"\n", argv[1]);
  //  strncpy(data, argv[1], SHM_SIZE);
  //} else
  //  printf("segment contains: \"%s\"\n", data);

}

void detach_memory(){
  /* detach from the segment: */
  if (shmdt(data) == -1) {
    perror("shmdt");
    exit(1);
  }
}