Cargo and your first program

Rust is installed with rustup, which manages toolchains (stable, beta, nightly) and keeps them updated with rustup update. It also installs rustc, the compiler, and Cargo, the build tool and package manager. In practice you almost never call rustc directly.

cargo new hello creates a package: a Cargo.toml manifest and src/main.rs. The manifest names the package, sets edition = "2024" (the language edition, which controls a few syntax and lint defaults) and lists dependencies.

The everyday commands:

• cargo run compiles in debug mode and runs the binary.
• cargo build --release builds an optimized binary into target/release/. Debug builds are fast to compile but can be 10-50x slower at runtime, so always benchmark release builds.
• cargo check type-checks without producing a binary. It is much faster, so use it constantly while editing.
• cargo fmt formats code and cargo clippy runs the linter; both are standard in real projects.

Every binary starts at fn main(). println! is a macro (note the !), which is how Rust supports format strings that are checked at compile time. Placeholders are {} for user-facing Display output and {:?} for Debug output, and you can put variable names inline: println!("{name}").

The compiler's error messages are unusually good. Read them fully: they usually point at the exact span and often suggest the fix.