In-class Exercise: Parent and Child Processes

grandparent.cpp

#include <cstdlib>
#include <iostream>

#include <sys/wait.h>
#include <unistd.h>

using std::cout;
using std::endl;

int main()
{
    auto first_child_fork_returned = fork();
    if (first_child_fork_returned == 0) {
        cout << "I am the first child." << endl;

        auto grandchild_fork_returned = fork();
        if (grandchild_fork_returned == 0) {
            cout << "I am the grandchild." << endl;
        } else { // grandchild_fork_returned > 0
            cout << "I am the first child and have started the grandchild." << endl;
            wait(NULL); // for grandchild
        }
    } else { // first_child_fork_returned > 0
        cout << "I am the parent and have started the first child." << endl;
        wait(NULL); // for first child

        auto second_child_fork_returned = fork();
        if (second_child_fork_returned == 0) {
            cout << "I am the second child." << endl;
        } else { // second_child_fork_returned > 0
            cout << "I am the parent and have started the second child." << endl;
            wait(NULL); // for second child
        }
    }

    return EXIT_SUCCESS;
}