Cargo: The Rust Build System

Building Rust programs with Cargo

What Is Cargo?

I’ve never liked Makefiles, so it’s a relief to discover that Rust has its own build tool and dependency manager. Cargo can build your program and it can even download any libraries/dependencies that your program needs, automatically.

Before getting started with Cargo, you might want to check your installation is up to date, by running rustup update.

The rustup tool will check for updates.

Building Programs with Cargo

We’ll be using the following Cargo commands to create, work with and build a program which I’ve arbitrarily called hello.

• cargo new hello

• cargo build

• cargo run

• cargo build —-release

• cargo run —-release

Open a terminal in a appropriate directory and run cargo new hello.

This will create a directory called hello. In there we can find a Cargo.toml config file and a src subdirectory. In the src subdirectory, Cargo has created a “hello world” program, in the file hello.rs.

It also initialises a git repository, which is handy if you use git.

To build the program, type cargo build.

This create a target subdirectory, and in there a debug subdirectory, which contains a debug version of your program.

You can run it in the normal way, by entering ./target/debug/hello, but you can more conveniently run it by executing cargo run.

When you change any code in the src directory, cargo run will automatically detect the changes and rebuild the program as necessary.

To build a release version you can execute cargo build —-release, and you can run it by executing cargo run —-release.

By itself, cargo run will run the debug version by default.