/*
 * Copyright 2007, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
 * Distributed under the terms of the MIT License.
 */


#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>


/*!
        wait() should wait only once. If any argument is given, waitpid() should return
        an error (and errno to ECHILD), since there is no child with that process group ID.
*/


int
child2()
{
        sleep(2);
        return 2;
}


//! exits before child 2
int
child1()
{
        setpgrp();
                // put us into a new process group

        pid_t child = fork();
        if (child == 0)
                return child2();

        sleep(1);
        return 1;
}


int
main(int argc, char** argv)
{
        bool waitForGroup = argc > 1;

        pid_t child = fork();
        if (child == 0)
                return child1();

        pid_t pid;
        do {
                int childStatus = -1;
                if (waitForGroup)
                        pid = waitpid(0, &childStatus, 0);
                else
                        pid = wait(&childStatus);
                printf("wait() returned %ld (%s), child status %d\n",
                        pid, strerror(errno), childStatus);
        } while (pid >= 0);

        return 0;
}