http://stackoverflow.com/questions/3667201/redirecting-in-c/3667321#3667321

scoped_cout_redirector.cpp

#include <iostream>
#include <fstream>

class scoped_cout_redirector
{
public:
    scoped_cout_redirector(const std::string& filename)
        :backup_(std::cout.rdbuf())
        ,filestr_(filename.c_str())
        ,sbuf_(filestr_.rdbuf())
    {
        std::cout.rdbuf(sbuf_);
    }

    ~scoped_cout_redirector()
    {
        std::cout.rdbuf(backup_);
    }

private:
    scoped_cout_redirector();
    scoped_cout_redirector(const scoped_cout_redirector& copy);
    scoped_cout_redirector& operator =(const scoped_cout_redirector& assign);

    std::streambuf* backup_;
    std::ofstream filestr_;
    std::streambuf* sbuf_;
};