Deno.copy

Copies from src to dst until either EOF (null) is read from src or an error occurs. It resolves to the number of bytes copied or rejects with the first error encountered while copying.

const source = await Deno.open("my_file.txt");
const bytesCopied1 = await Deno.copy(source, Deno.stdout);
const destination = await Deno.create("my_file_2.txt");
const bytesCopied2 = await Deno.copy(source, destination);