A quick test for my answer here https://stackoverflow.com/a/61175504/1585957

stdout_stderr.cpp

#include <iostream>
#include <thread>
#include <chrono>
using namespace std;

int main(int argc, char const *argv[])
{
	cout << "Hello, world";
	this_thread::sleep_for (chrono::seconds(5));
	cerr << "this is an error";
	return 0;
}