Hello, World in Rust

Start quickly with cargo, Rust’s build tool and package manager.

Using cargo (recommended)

Create a new binary crate and run it.

cargo new hello
cd hello
cargo run

cargo run compiles and runs src/main.rs in debug mode. For a faster binary, use release:

cargo run --release

main function and println!

The entry point is a main function. Use println! (a macro) for output.

fn main() {
    println!("Hello, world!");
}

Format with {} placeholders and arguments.

let name = "Rust";
let version = 1.76;
println!("Hello, {} v{}", name, version);
println!("{name} v{version:.1}"); // named capture (Rust 1.58+)

Debug printing

Use {:?} for debug output of types that implement Debug.

let nums = vec![1, 2, 3];
println!("nums = {:?}", nums);

stderr and eprintln!

Write to stderr with eprintln!.

eprintln!("warning: something happened");

rustc (quick compile)

Compile a single file without Cargo (useful for tiny experiments).

rustc main.rs && ./main

Format and lint

Keep code consistent and idiomatic.

cargo fmt     # rustfmt
cargo clippy  # lints and suggestions

Comments and docs

// Line comment
/* Block comment */
/// Doc comment for items (appears in rustdoc)

Generate docs: cargo doc --open.

Summary

• Use cargo new and cargo run to get started
• println! formats output; {:?} prints Debug
• Format with cargo fmt; lint with cargo clippy