The following code example is taken from the book
Object-Oriented Programming in C++
by Nicolai M. Josuttis, Wiley, 2002
© Copyright Nicolai M. Josuttis 2002
#include <iostream>
#include <fstream>
#include <string>
void redirect(std::ostream&,const std::string&);
int main()
{
std::cout << "first line" << std::endl;
redirect(std::cout, "redirect.txt"); // redirect cout to redirect.txt
std::cout << "last line" << std::endl;
}
void redirect(std::ostream& strm, const std::string& filename)
{
// open file (with buffer) for writing
std::ofstream file(filename.c_str());
// save output buffer of the passed stream
std::streambuf* strm_puffer = strm.rdbuf();
// redirect output to the file
strm.rdbuf(file.rdbuf());
file << "line is directly written to the file" << std::endl;
strm << "line is written to the redirected stream"
<< std::endl;
// restore old output buffer of the passed stream
strm.rdbuf(strm_puffer);
} // closes the file and the redirected buffer