[Rust] Hello World with Cargo

This post is written by YoungJ-Baek

This post is written referring to the official documentation

This post is based on M1 Macbook Pro 14 inch, macOS Ventura 13.0

1. Preface

We already printed Hello, world with rustc command to compile and run in last post. However, there is another way to compile and run, cargo. The relationship between rustc and cargo is similar to make and cmake in C/C++.

2. Print Hello World with Cargo

2.1. Prepare Project Folder

First, go back to your projects directory, and then type the command below to make other folder for cargo.

Command

$ cargo new hello_cargo --bin
$ cd hello_cargo

First line means you will create a new project named hello_cargo, not a library but a binary purpose. Then, there will be two files and one directory, Cargo.toml, and src directory including main.rs file in it.

2.2. Cargo.toml

If you generate Rust project with cargo, you will manage it with Cargo.toml file. In this file, you can put all the information of the project including name, version, and authors. Moreover, you can manage all the dependencies of the project in this file. For now, there is no dependency, but we will add something at the next post.

Cargo.toml

[package]
name = "hello_cargo"
version = "0.1.0"
edition = "2021"
authors = ["YoungJin-Baek <qordudwls1@gmail.com>"]

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

By the way, cargo already generate main file with some example code to print Hello, world. So, you do not have to add anything for it. Now, you are ready to print Hello, world with cargo.

2.3. Compile and Run (1)

Third, you are now ready to compile the file and run it. Cargo compiles and runs the files under src directory. So, all you have to do for compile and run is to add files under the src directory. You do not have to learn other things unlike cmake.

Compile and Run

$ cargo build
   Compiling hello_cargo v0.1.0 (/Users/youngjin/Desktop/projects/hello_cargo)
    Finished dev [unoptimized + debuginfo] target(s) in 2.62s

Run

$ ./target/debug/hello_cargo

Result

Hello, world!

Note that compiled file is located at target/debug/.

2.4. Compile and Run (2)

Cargo provides another way to compile and run the project. You do not have to compile and run seperately, but you can do both of them spontaneously. All you have to do is typing simple command.

Compile and Run

$ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.02s
     Running `target/debug/hello_cargo`

Result

Hello, world!

In this example, there is no log related to compiling. It is because we have already compile the project before, and there is no change after that. So, cargo do not have to build the project again, instead, it runs the file.

2.5. Cargo Check

Cargo provides very interesting function. It checks whether the project is able to be compiled or not. So, if you want to check there is no error, you can use this command. Also, it does not generate binary file for the result, it saves the time via not generating the file.

Cargo Check

$ cargo check
    Checking hello_cargo v0.1.0 (/Users/youngjin/Desktop/projects/hello_cargo)
    Finished dev [unoptimized + debuginfo] target(s) in 0.33s

2.6. Build for Release

You can make release version via cargo, too. It is very simple, but takes longer time compared to building for debug. So, when you are ready to release your project, use the command below. Otherwise, use the command in chapter 2.3 or 2.4.

Build for Release

$ cargo build --release
   Compiling hello_cargo v0.1.0 (/Users/youngjin/Desktop/projects/hello_cargo)
    Finished release [optimized] target(s) in 2.29s

Unlike building for debug, the result file will be generated in target/release directory. You can run this file when you need to benchmark your software. Everything will have been optimized via cargo.