freopen() equivalent for c++ streams

#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/

This newsgroup posting explores your options.

This is system dependent and the poster didn't indicate the system, but cin.clear() should work. I have tested the attached program on a UNIX system with AT&T version's of iostreams.

#include <iostream.h> int main() { for(;;) { if ( cin.eof() ) { cout << "EOF" << endl; cin.clear(); } char c ; if ( cin.get(c) ) cout.put(c) ; } } 

Yes, that works okay in cfront and TC++. In g++ where the problem first arose an additional action is required:

 cin.clear(); rewind ( _iob ); // Seems quite out of place, doesn't it? // cfront also accepts but doesn't // require this rewind. 

Though I note that this was in 1991, it should still work. Remember to use the now-standard iostream header, not iostream.h.

(BTW I found that post with the Google search terms "reopen cin c++", second result.)

Let us know how you get on. You could also just use freopen.