#include <iostream>
#include <fstream>
using namespace std;

void redirect(ostream&);

int main()
{
    cout << "the first row" << endl;

    redirect(cout);

    cout << "the last row" << endl;
}

void redirect (ostream& strm)
{
    ofstream file("redirect.txt");
    
    // save output buffer of the stream
    streambuf* strm_buffer = strm.rdbuf();

    // redirect ouput into the file
    strm.rdbuf (file.rdbuf());

    file << "one row for the file" << endl;
    strm << "one row for the stream" << endl;

    // restore old output buffer
    strm.rdbuf (strm_buffer);

}    // closes file AND its buffer automatically