C No ouput when Trying to run two functions at once using threads-CodePudding

Hello i am trying to run two functions at the same time. Because i want to learn to make a timer or countdown of some kind.

And i have an idea on how to do so. But when i create two threads.

I get no output in my console application.

Here is my code.

#include <iostream>
#include <Windows.h>
#include <thread>
#include <random>
#include <string>

void timer()
{
    int x{ 0 };
    if (x < 1000)
    {
        std::cout << x  ;
        Sleep(1000);
    }

}
void timer2()
{
    int x{ 0 };
    if (x < 10000)
    {
        std::cout << x  ;
        Sleep(1000);
    }
     
}
int main()
{
    std::thread one(timer);
    std::thread two(timer2);
     
    one.detach();
    two.detach();
    return 0;
}

CodePudding user response：

You should use join instead of detach. Otherwise, the main thread won't wait for the other threads and the program will exit almost immediately. You can use std::this_thread::sleep_for instead of Sleep to make the code portable (no Windows.h required).

#include <iostream>
#include <thread>
using namespace std::chrono_literals;

void timer()
{
    int x{ 0 };
    if (x < 1000)
    {
        std::cout << x  ;
        std::this_thread::sleep_for(1s);
    }

}
void timer2()
{
    int x{ 0 };
    if (x < 10000)
    {
        std::cout << x  ;
        std::this_thread::sleep_for(1s);
    }
     
}
int main()
{
    std::thread one(timer);
    std::thread two(timer2);
     
    one.join();
    two.join();
    return 0;
}

CodePudding user response：

You need to flush the output. C won't output anything until it flushes. You can achieve this by

cout << x   << "\n";

cout << x   << std::flush;

according to this answer