`cargo run` builds and runs a Rust program in a Cargo project. If the program uses an external crate, Cargo brings in that crate and the other crates it needs before starting the program. section 18.1.1
To try it with an external crate:
- Create a project with `cargo new my_project`. Its `src/main.rs` is where the program starts. section 18.1.1
- Add `rand = "0.8.5"` under `[dependencies]` in `Cargo.toml`, then use `rand` in your code. section 16.5.1 section 18.1.1
- Type `cargo run` to build the project and run it. section 18.1.1
Compiling rand_core v0.6.4
Compiling rand_chacha v0.3.1
Compiling rand v0.8.5
Compiling random_test v0.1.0 (C:\rust\random_test)
Finished dev [unoptimized + debuginfo] target(s) in 2.61s
Running `target\debug\random_test.exe`
The first run shows Cargo compiling `rand` and crates it depends on, then running the program. section 18.1.1
After a small code change, run the same command again. Crates that are already available need not be recompiled, so this run can be quicker. Use `cargo check` when you only want to see whether the code compiles; use `cargo run` to test it out. section 18.1.2 section 18.5
