Question

Is it possible to create a boost::thread and run it in the background (as a daemon)?
I am trying to the following but my thread dies when main exits.

/*
 * Create a simple function which writes to the console as a background thread.
 */
void countDown(int counter) {
    do {
        cout << "[" << counter << "]" << endl;
        boost::this_thread::sleep(seconds(1));
    }while(counter-- > 0);
}

int main() {
    boost::thread t(&countDown, 10);

    if(t.joinable()) {
        cout << "Detaching thread" << endl;
        t.detach(); //detach it so it runs even after main exits.
    }

    cout << "Main thread sleeping for a while" << endl;
    boost::this_thread::sleep(seconds(2));
    cout << "Exiting main" << endl;
    return 0;
}

[rajat@localhost threads]$ ./a.out

Detaching thread

Main thread sleeping for a while

[10]

[9]

Exiting main

[rajat@localhost threads]$

Answer 1

When your main() exits all other threads of the process are terminated (assuming Linux, can’t say for Windows).

Why not just join() that background thread at the end of the main()? Or even better – use the main thread as the “daemon” thread?