[ACCEPTED]-freopen() equivalent for c++ streams-io
freopen also works with cin and cout. No need to search 6 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 5 object cin controls input from a stream 4 buffer associated with the object stdin, declared 3 in
<cstdio>.
So according to the standard, if we 2 redirect stdin it will also redirect cin. Vice versa 1 for cout.
#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/
0
This newsgroup posting explores your options.
This 13 is system dependent and the poster didn't 12 indicate the system, but cin.clear() should 11 work. I have tested the attached program 10 on a UNIX system with AT&T version's 9 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 8 and TC++. In g++ where the problem first 7 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 6 I note that this was in 1991, it should 5 still work. Remember to use the now-standard 4 iostream header, not iostream.h.
(BTW I found that post with 3 the Google search terms "reopen cin 2 c++", second result.)
Let us know how 1 you get on. You could also just use freopen.
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