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

void  err_sys(char * msg) {
  printf("%s \n", msg);
  exit(-1); 
}

int
main(void)
{
	pid_t	pid;

	if ( (pid = fork()) < 0)
	  err_sys("fork error");
	else if (pid == 0) {		/* first child */
		if ( (pid = fork()) < 0)
		  err_sys("fork error");
		else if (pid > 0)
			exit(0);	/* parent from second fork == first child */

		/* This is the second child; its parent becomes init as soon
		   as our real parent -the first child-  calls exit() in the statement
		   above.
		   Here's where we'd continue executing, knowing that when
		   we're done, init will read our status. */

		sleep(2);
		printf("second child, parent pid = %d\n", getppid());
		exit(0);
	}

	if (waitpid(pid, NULL, 0) != pid)	/* wait for first child */
		err_sys("waitpid error");

	/* This is the parent (the original process); it continues executing,
	   knowing that it's not the parent of the second child. */
	system("ps");
	
	exit(0);
}