lst-0005-book.cpp
// https://godbolt.org/z/P1fn5q8z8
// Call this program with 'prog.exe > file.txt', for example.
#include <iostream> // cout, cerr
int main() {
std::cout << "Output to cout\n"; // is output after 'file.txt'
std::cerr << "Error message!\n"; // still appears on the console
std::cout << "Normal output again\n"; // back into the file
}