#include <stdio.h>
#include <sys/ipc.h>
#include <time.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/wait.h>  /* Needed for the wait function */
#include <unistd.h>    /* needed for the fork function */
#include <string.h>    /* needed for the strcat function */
#include <stdio.h>
#include <stdlib.h>
#include <semaphore.h>
#include <stdint.h>
#include <sys/mman.h>
#define SHMSIZE 27

int main(){
sem_t *m;
if((m = sem_open("mysemaphore",O_CREAT,0644,1)) == SEM_FAILED)
{
	perror("Error");
        exit(1);
}
int shmid;
int *shm;

sem_init(m,1,1);


if (fork() == 0)
{
	int i;
        shmid = shmget(2009,SHMSIZE,0);
        shm = (int *)shmat(shmid,0,0);
        *shm =1000;
	while(1)
 	{
	  sem_wait(m);
          *shm = *shm -1;
          printf("val_child=%d\n",*shm);
          sem_post(m);
	}
	  shmdt(shm);
}
else
{
	shmid = shmget(2009,SHMSIZE,0666 | IPC_CREAT);
        shm = (int *)shmat(shmid,0,0);
        while(1)
	{
		sem_wait(m);
		*shm = *shm+1;
		printf("val_parent%d\n",*shm);
		sem_post(m);
	}
	shmdt(shm);
}
return 0;
}