Boilerplate

In the previous section, we used cargo new to create a Rust package, which is the most common way to create a package. Running this command generated some boilerplate code. When we used cargo run, a target directory was created and the Rust compiler rustc was invoked, generating compiler-related files and an executable binary within the target directory.

Let's clean everything up with cargo clean and return to the boilerplate. The cargo clean command removes the target directory where all the generated code resides. After running cargo clean, we're left with the boilerplate.

$ cargo clean
     Removed 23 files, 2.9MiB total

.
+ Cargo.lock
+ Cargo.toml
+ src
  + main.rs

For now, we'll focus on main.rs and discuss Cargo.lock and Cargo.toml later.

main.rs

main.rs is a Rust source file that gets created as part of a package. It includes a function named main that serves as the program entry point.

The contents of main.rs:

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

Some of the syntax should look familiar:

• Blocks of code are surrounded by curly braces {}.
• Statements end with a semicolon ;.
• Function parameters are enclosed in parentheses ().
• String literals are enclosed in double quotes "".

What may not be familiar:

• fn is the keyword used to declare a function.
• println! is actually a macro, denoted by the ! suffix.

Summary

In this section, we:

• Explored the boilerplate code generated by cargo new.
• Reviewed some basic Rust syntax.

Next

Let's dive into building our rustle program. We'll start by setting up the basic structure and then gradually add more functionality.