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:

  • 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 explain how to use these traits and their methods, cover the reader and writer types shown in the figure, and show other ways to interact with files, the terminal, and the network.

A diagram that shows the three traits, Read, BufRead, and Write,             and a few examples of types that implement each one. Some types, like File,             implement both Read and Write.
Figure 18-1. Rust’s three main I/O traits and selected types that implement them

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 input stream ...

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