mutex.cpp

#include <array>
#include <thread>
#include <iostream>

int main() {
    constexpr auto n_threads = 10u;
    std::array<std::thread, n_threads> threads;
    std::mutex cout_mutex;

    const auto hello = [&cout_mutex](int i) {
        // Uncommenting this line will randomly interleave all the threads' outputs.
        std::lock_guard<std::mutex> cout_lock(cout_mutex);
        std::cout << "Hello from thread " << i << '\n';
    };

    for (auto i = 0u; i < n_threads; ++i) {
        threads[i] = std::thread(hello, i);
    }

    for (auto i = 0u; i < n_threads; ++i) {
        threads[i].join();
    }

    return 0;
}