simple example for using cpp thread / mutex / condition_variable to toggle running a daemon in the background

daemon.cpp

#include <iostream>
#include <condition_variable>
#include <thread>
#include <chrono>
#include <mutex>
#include <atomic>

std::condition_variable activity_cv;
std::mutex activity_mutex;
std::atomic<bool> run_daemon = false;

void process() {

    std::this_thread::sleep_for(std::chrono::milliseconds(200));
    std::cout << "Process!" << std::endl;
}

void daemon() {
    while(true) {
        std::unique_lock<std::mutex> lk(activity_mutex);
        std::cerr << "Waiting for permission to run_daemon \n";
        activity_cv.wait(lk, []{return bool(run_daemon);});
        while(run_daemon) {
            process();
        }
    }
}
 
 
int main() {
    std::thread daemon_thread(daemon);
    while(true) {
        if(run_daemon) {
            std::this_thread::sleep_for(std::chrono::seconds(1));
        } else {
            std::this_thread::sleep_for(std::chrono::seconds(2));
        }


        run_daemon = !run_daemon;//toggle running daemon
        activity_cv.notify_all();
    }
}