#include<stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>

int main()
{
   pid_t pid;
   int x = 3;
   pid = fork();        /* fork another process */

   if (pid < 0)         /* Forking error! */
      {   exit(-1);   }
   else if (0 == pid)   /* Child process */ 
      {
	// Child process sleeps -- does nothing -- for 2 seconds.
	sleep(2);
	// Child prints its value of x.
	printf("Child x = %d\n", x);  
	exit(0);
      }
   else                 /* pid > 0: Parent process */
      {   
	// Parent changes value of x.  Because this is *after* the fork(),
	//  the child process will retain its unchanged value of x.
	x = 4;
	printf("Parent x = %d\n", x);
	wait(NULL);
	exit(0);
      }
}