freopen() equivalent for c++ streams

Question

When programming with c-style i/o I sometimes use freopen() to reopen stdin for testing purposes so that I don't have to retype the input over and over. I was wondering if there is an equivalent for c++ i/o streams. Also, I know that I can use pipes to redirect it on the command line/terminal/whateveritis but I was wondering if there was a way to do it inside my code (because as you can see, I'm not very knowledgeable about the cl/t/w).

Answer 1

freopen also works with cin and cout. No need to search for something new.

freopen("input.txt", "r", stdin); // redirects standard input freopen("output.txt", "w", stdout); // redirects standard output  int x; cin >> x; // reads from input.txt cout << x << endl; // writes to output.txt 

Edit: From C++ standard 27.3.1:

The object cin controls input from a stream buffer associated with the object stdin, declared in <cstdio>.

So according to the standard, if we redirect stdin it will also redirect cin. Vice versa for cout.

Answer 2

#include <iostream> #include <fstream>  int main() {    // Read one line from stdin   std::string line;   std::getline(std::cin, line);   std::cout << line << "\n";    // Read a line from /etc/issue   std::ifstream issue("/etc/issue");   std::streambuf* issue_buf = issue.rdbuf();   std::streambuf* cin_buf = std::cin.rdbuf(issue_buf);   std::getline(std::cin, line);   std::cout << line << "\n";    // Restore sanity and read a line from stdin   std::cin.rdbuf(cin_buf);   std::getline(std::cin, line);   std::cout << line << "\n"; } 

http://www.cplusplus.com/reference/iostream/ios/rdbuf/