Tips

CLI Apps

std::env::args() returns an iterator to command line arguments.
std::process::exit(1) terminates the program with some exit code.
keeping src/main.rs short is a good practice. The logic should be moved to separate files like src/lib.rs. That also makes the logic testable (binary crates are not testable).
eprintln! macro prints to stderr.
a clap cargo is useful for defining CLI arguments

Documentation

Rust has built-in documentation for code. Our code can be documented as well.

Documenting files

Here’s an example:

//! # My Crate
//!
//! `my_crate` is a collection of utilities to make performing certain
//! calculations more convenient.

It is some more general documentation about our crate. It could appear in the src/lib.rs.

Documenting functions

Here’s an example:

/// Adds one to the number given.
///
/// # Examples
///
/// ```
/// let arg = 5;
/// let answer = my_crate::add_one(arg);
///
/// assert_eq!(6, answer);
/// ```
pub fn add_one(x: i32) -> i32 {
  x + 1
}

The documentation should appear just before the documented element.

Cargo

We generate the docs with cargo doc. It runs rustdoc internally. The HTML docs are placed in target/doc.

Tests

Documentation might also contain example code. That code is run automatically with cargo test. In the example code shown previousy, the example code would be run.

← Testing