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Exercise: Hello World

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With Rust installed, you're ready to start coding. Let's write a program that prints "Hello, world!" to the console.

Create a new directory to organize your code

Start by creating a directory for storing all the code in this learning path (rust-learning-path), and then creating a new subdirectory to keep the source code for this exercise.

For the Windows command prompt, run the following commands:

mkdir "%USERPROFILE%\rust-learning-path"
cd /d "%USERPROFILE%\rust-learning-path"
mkdir hello-world
cd hello-world

For Linux, macOS, and PowerShell on Windows, run the following commands:

mkdir ~/rust-learning-path
cd ~/rust-learning-path
mkdir hello-world
cd hello-world

Write your first Rust program

Next, create a new file named main.rs and use your editor to write the following code into it:

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

Compile and run your program

Your source code is ready. Now it's time to compile your program into an executable file. Return to your terminal window and enter the following commands to compile and run the file.

On Windows, run the following commands:

rustc main.rs
.\main.exe

If you're on Linux or macOS, run the following commands:

rustc main.rs
./main

You should see the following output:

Hello, world!

Create a project with Cargo

Now let's use Cargo to write and run the same program.

Note

The commands in the following sections work on all platforms.

To start, we use Cargo to make a new project.

Make sure your terminal is at your rust-learning-path directory, and run the following command:

cargo new hello-cargo

This command generates a new directory named hello-cargo with a src subdirectory and adds two files:

hello-cargo/
     Cargo.toml
     src/
         main.rs

• The Cargo.toml file is the manifest file for Rust. It's where you keep metadata for your project and also any dependencies.
• The main.rs file in the src subdirectory is where you write your application code.

Notice that the cargo new command generated a boilerplate "Hello, world!" project for you.

Build and run your program with Cargo

To execute the boilerplate program, move into the new directory hello-cargo, and then use the cargo run command.

Run the following commands in your terminal:

cd hello-cargo
cargo run

You should see the following output in your terminal:

  Compiling hello-cargo v0.1.0 (/tmp/.OFUp/hello-cargo)
    Finished dev [unoptimized + debuginfo] target(s) in 1.59s
      Running `target/debug/hello-cargo`

Hello, world!

Cargo has built and executed your executable.

Congratulations, you've written your first Rust program and learned how to initialize your first Rust project with Cargo!

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