title: std::string formatting like sprintf
body: <p>I have to format <a href="http://en.cppreference.com/w/cpp/string/basic_string"><code>std::string</code></a> with <a href="http://en.cppreference.com/w/cpp/io/c/fprintf"><code>sprintf</code></a> and send it into file stream. How can I do this?</p>