// CS 450: Process example 2: fork, timed wait
// version 2013-01-22 11:42 am
//
#include <stdio.h>
#include <unistd.h>    // fork
#include <stdlib.h>    // exit
#include <sys/errno.h> // global error number
#include <sys/wait.h>  // wait

// Prototype for child processes
	pid_t child(int child_nbr, int sleeptime);

int main(int argc, char *argv[]) {
    pid_t pid_child1, pid_child2, exited_child;
    int i, child_nbr, status;

    // Child 1 should sleep 3 sec; child 2 7 sec
    //
    pid_child1 = child(1, 3);
    pid_child2 = child(2, 7);
    printf("This is the parent\n");

    // Wait twice: Each time, wait for a
    // child and print out its nbr & status
    for (i = 0 ; i < 2 ; i++) {
        exited_child = wait(&status);
        child_nbr = (exited_child == pid_child1 ? 1 : 2);
        printf("Child %d pid %d exited with status %d\n",
        	child_nbr, exited_child, status );
    }
    return 0;
}

// Child prints its pid and sleeps for a number
// of seconds
//
pid_t child(int child_nbr, int sleeptime) {
	pid_t pid = fork();

	if (pid > 0) {  // Parent returns
		return pid;
	}
	else if (pid == -1) {  // Fork failed !?
		fprintf(stderr, "Fork %d failed with error %d\n",
			child_nbr, errno );
		exit(1);
	}

	// We're the child process
	printf("Child %d, pid %d\n", child_nbr, getpid());
	sleep(sleeptime);
	exit(0);
}


// Sample output
//
// This is the parent
// Child 1, pid 2055
// Child 2, pid 2056
// Child 1 pid 2055 exited with status 0
// Child 2 pid 2056 exited with status 0