How to override cout in C++?

Question

I have a requirement, I need to use printf and cout to display the data into console and file as well. For printf I have

Answer 1

If you have another stream buffer, you can just replace std::cout's:

std::cout.rdbuf(some_other_rdbuf);

See http://en.cppreference.com/w/cpp/io/basic_ios/rdbuf.