how-to-redirect-cin-and-cout-to-files

#include <iostream> #include <fstream> #include <string> void f() { std::string line; while(std::getline(std::cin, line)) //input from the file in.txt { std::cout << line << "\n"; //output to the file out.txt } } int main() { std::ifstream in("in.txt"); std::streambuf *cinbuf = std::cin.rdbuf(); //save old buf std::cin.rdbuf(in.rdbuf()); //redirect std::cin to in.txt! std::ofstream out("out.txt"); std::streambuf *coutbuf = std::cout.rdbuf(); //save old buf std::cout.rdbuf(out.rdbuf()); //redirect std::cout to out.txt! std::string word; std::cin >> word; //input from the file in.txt std::cout << word << " "; //output to the file out.txt f(); //call function std::cin.rdbuf(cinbuf); //reset to standard input again std::cout.rdbuf(coutbuf); //reset to standard output again std::cin >> word; //input from the standard input std::cout << word; //output to the standard input }