Standart input stream redirection (C++)

Question

So I've heard it is possible to redirect the input stream to file for example. How can I do so?
I've tried writing
#include <iostream>
#include <fstream>
.....*code*.....
ofstream file(data.txt);
cout = file;
cout << "*data*";
But it didn't compile because of line "cout = file", where it says that operator = is private.
I am sure it can be done in a simular way, but I don't now how exactly... Help me please.

Answer 1

https://en.cppreference.com/w/cpp/io/basic_ios/rdbuf

Answer 2

Oh, my bad. I meant output. Thank you for your answers! rdbuf function also works really good.