Programming Rust, 3rd Edition

Chapter 17. Input and Output

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Doolittle: What concrete evidence do you have that you exist?

Bomb #20: Hmmmm... well... I think, therefore I am.

Doolittle: That’s good. That’s very good. But how do you know that anything else exists?

Bomb #20: My sensory apparatus reveals it to me.

Dark Star

Input and output are the limbs that turn the disembodied logic of a program into something that can reach out and interact with the world. Most of the time, that means working with filesystems and network interfaces, but there are more exotic types of I/O, too.

As it often strives to do, Rust’s standard library makes the easy cases easy. Reading a UTF-8 formatted text file (or HTML document, or CSV, or what have you) is as easy as calling std::fs::read_to_string:

let contents = std::fs::read_to_string("file.txt")
    .expect("Unable to read file");

Convenience functions like this make it easy to write lots of programs, but they’re all built on top of a relatively simple foundation of two I/O traits: Read ...