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

int main()
{
  pid_t prid;  // process id.

  x = 3;        
  printf("in main:\n");

  prid = fork();  // fork child process
  // prid == 0 if you're child process, otherwise prid== pid of child

  if (prid == 0)  // i'm child
    {  x++;
       printf("I'm the child, x==%d\n",x);   
    }
  else   // i'm parent
    {  x++;
       printf("I'm parent, x==%d\n",x);
    }
 
  exit(0);
}