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Reading & Defining `cargo.toml`

If Rust is installed on your system, then cargo by default is installed. cargo is Rust's package management system and can be called from the command line.

Creating a new project with Cargo​

Create a new project using cargo using the cargo new command. You will need to have your command line/terminal open. For the sake of this course, let's call the project first-cargo, which will create a new directory with your Rust project within:

cargo new first-cargo
cd first-cargo/

Upon running tree or ls -R, the file structure is revealed to be the following:

.
├── Cargo.toml
└── src
    └── main.rs

2 directories, 2 files

  • src/ is where your project lives and contains the source of your Rust project. main.rs is where you can and will write executable code.

  • Cargo.toml is how your Rust project manages project metadata, dependencies, and build options.

Understanding Cargo.toml​

Cargo.toml is written in the TOML format, and specifies metadata for your Rust project. Upon inspecting our project, first-cargo's Cargo.toml it should look relatively barebones:

[package]
name = "first-cargo"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

Each section is defined by square brackets ([]) followed by the name within (i.e., [package]). Keys are determined by the name, followed by an equals sign (=) and the value as text in double quotes (i.e., name = "first-cargo").

  • [package] - Specifies the name of the package, version of the binary, and the Rust edition used.

  • [dependencies] - Specifies a list of local or remote external dependencies.

Building & Running with Cargo​

Running cargo build within any directory with Cargo.toml will result in an attempt to build the project. This merely builds the project and generates a target/ folder with the compiled binary.

Compiling first-cargo v0.1.0 (/rust-course/first-cargo)
 Finished dev [unoptimized + debuginfo] target(s) in 1.09s

Running cargo run will both build the project, as well as run the binary.

Finished dev [unoptimized + debuginfo] target(s) in 0.03s
 Running `target/debug/first-cargo`
Hello, world!