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



int main(int argc, char**argv) {
  pid_t pid = fork();
  if(pid < 0) { abort(); }
  if(pid > 0) {
    /* P1 */
    printf("[%d] I'm P1. My PPID=%d\n", getpid(), getppid());
  } else {
    /* P2 */
    sleep(1);
    pid = fork();
    if( pid < 0) { abort(); }
    if(pid > 0) {
      /* P2 */
      printf("[%d] I'm P2. My PPID=%d\n", getpid(), getppid());
    } else {
      /* P3 */
      sleep(1);
      pid = fork();
      if( pid < 0) { abort(); }
      if(pid > 0) {
	/* P3 */
	printf("[%d] I'm P3. My PPID=%d\n", getpid(), getppid());
      } else {
	/* P4 */
	printf("[%d] I'm P4. My PPID=%d\n", getpid(), getppid());
	system("ps f");
      }
    }
  }

  return EXIT_SUCCESS;
}