Cargo and crates
When projects get large, a usual practice is to refactor code into smaller, more manageable units as modules or libraries. You also need tools to render documentation for your project, how it should be built, and what libraries it depends on. Furthermore, to support the language ecosystem where developers can share their libraries with the community, an online registry of some sort is often the norm these days.
Cargo is the tool that empowers you to do all these things, and https://crates.io is the centralized place for hosting libraries. A library written in Rust is called a crate, and crates.io hosts them for developers to use. Usually, a crate can come from three sources: a local directory, an online Git repository like GitHub, or a hosted crate registry like crates.io. Cargo supports crates from all of these sources.
Let's see Cargo in action. If you ran rustup, as described in the previous chapter, you will already have cargo installed, along with rustc. To see what commands...
