Programming Rust

Chapter 18. Input and Output

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

Rust’s standard library features for input and output are organized around three traits—Read, BufRead, and Write—and the various types that implement them:

• Values that implement Read have methods for byte-oriented input. They’re called readers.

• Values that implement BufRead are buffered readers. They support all the methods of Read, plus methods for reading lines of text and so forth.

• Values that implement Write support both byte-oriented and UTF-8 text output. They’re called writers.

Figure 18-1 shows these three traits and some examples of reader and writer types.

In this chapter, we’ll show how to use these traits and their methods, the various types that implement them, and other ways to interact with files, the terminal, and the network.

Figure 18-1. Selected reader and writer types from the Rust standard library

Readers and Writers

Readers are values that your program can read bytes from. Examples include:

• Files opened using std::fs::File::open(filename)

• std::net::TcpStreams, for receiving data over the network

• std::io::stdin(), for reading from the process’s standard ...