#include <iostream>  // std::cout, std::endl;
#include <cstdlib>   
#include <cmath>    
#include <csignal>
#include <thread>   // std::this_thread::sleep_for
#include <chrono>   // std::chrono::secnds


std::thread::id main_thread_id = std::this_thread::get_id();

void r1()
{
    for(;;){
        std::cout<<"thread t1 running  ID:"<< std::this_thread::get_id() <<std::endl;
        std::this_thread::sleep_for (std::chrono::seconds(1));
    }
}

void r2(int x)
{
    for(;x > 0; x--)
    {
        std::cout<<"thread t2 running:"<<x <<"  ID:"<< std::this_thread::get_id() <<std::endl;
        std::this_thread::sleep_for (std::chrono::seconds(1));
        //std::this_thread::sleep_for (std::chrono::nanoseconds(100));
    }
}


int main(int argc, char **argv)
{

    if(main_thread_id == std::this_thread::get_id()) {
        std::cout<<"This is main thread."<<std::endl;
    } else {
        std::cout<<"Not main thread."<<std::endl;
    }

    std::thread t1(r1);
    std::thread t2(r2, 20);

    std::cout<<"main and r1, r2 runinng now."<<std::endl;
    t1.join();
    t2.join();


    std::cout<<"runinng finished."<<std::endl;


    return 0;
}

编译：
$g++ -std=c++11 thread.cc -o thread -lpthread
$./thread