Cargo

Cargo is a build system (turns Rust code into executable binaries) and a package manager (downloads and compiles project’s dependencies).

cargo new creates a new project from a standard template. There’s a Cargo.toml file and the src/ directory.

Toml file

The Cargo.toml files contains project’s metadata (like npm’s project.json). After running the project, Cargo.lock is created as well, which works like project-lock.json of npm. It specifies the exact version numbers of all the dependencies. This way, future builds are reliable.

Running

cargo run does the following:

compiles the code in debug mode (for maximal error information) using cargo build
executes the binary

Also, a lot of new files are added to the project. They are all managed by cargo.

cargo run --release compiles a release build.

Release Profiles

Rust apps have two profiles:

dev (used with cargo build) - good defaults for development
release (used with cargo build --release) - good defaults for release builds

These profiles can be customized in the Cargo.toml file. Example:

[profile.dev]
opt-level = 0

[profile.release]
opt-level = 3

The dev profile has 0 optimizations (because we want it to compile fast even though the code runs slower).

Other commands

cargo build - downloads dependencies and compiles the code. It uses the “rustc” compiler behind the scenes.
cargo doc - builds HTML documentation for every dependency in the current project.
cargo init - initaites a Rust project with pre-existng files in it. cargo create would create a project from scratch.
cargo add - adds crates. This subcommand needs to be installed first with cargo install cargo-edit.

Crates

Packages are called crates. The open-source ones are shared at https://crates.io.

Binary crates

Binary crates might be installed with cargo install some-crate. They will be installed in $HOME/.cargo/bin.

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