#include <sys/signal.h>

int write(int,char*,int);
int fork(void);
int getpid(void), getppid(void);

int main()
{

int pid;

printf("pid of old process is %d\n",getpid());

if ((pid=fork())==0) {
	/* child code */
	write(1,"inside child\n",13);
	printf("child's pid = %d\n",getpid());
	printf("pid in child (should be zero) %d\n",pid);
	printf("pid of parents' id = %d\n",getppid());
	}
else {
	/* parent's code */
	printf("inside parent; pid of child is %d\n",pid);
	printf("pid of parents' parent = %d\n",getppid());
	sleep(20);
	}

/* common code */
}