/*
 * fork/wait example.
 * Godmar Back <gback@cs.vt.edu>
 * CS 3204 Fall 2006
 */
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

int
main(int ac, char *av[])
{
    pid_t child = fork();
    if (child < 0)
	perror ("fork"), exit(-1);
	
    if (child != 0) {	// parent takes 'then' branch
        wait(NULL);	// wait for our only child
        printf ("I'm the parent %d, my child is  %d\n", 
            getpid(), child);
    } else {		// child takes 'else' branch
        printf ("I'm the child  %d, my parent is %d\n", 
            getpid(), getppid());

	// now changing program
        execl("/bin/echo", "echo", "Hello, World", NULL);
	// should only get here if "execl" failed for some reason
	perror ("execl");
	exit (-1);
    }
    return 0;
}