Question

It must be pure c++, I know about system("copy c:\\test.txt d:\\test.txt"); but I think it’s the system function, not c++ solution, or I can mistakes?

Answer 1

How about std::fstream? Open one for reading and another for writing, and use std::copy to let the standard library handle the copying.

Something like this:

void copy_file(const std::string &from, const std::string &to)
{
    std::ifstream is(from, ios::in | ios::binary);
    std::ofstream os(to, ios::out | ios::binary);

    std::copy(std::istream_iterator<char>(is), std::istream_iterator<char>(),
              std::ostream_iterator<char>(os));
}