Conf42 Rustlang 2023 - Online

Learn Rust By Building CLI Tools

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Want to finally graduate from “learning” Rust to really “building” cool things? These exercises and examples allow you to explore the language in a low-stakes setting where you can accomplish your goals quickly and add skills to your Rust tool box.


  • Learn Rust by building CLI tools. Use these small exercises as a way to practice not just writing the rust code, but also to practice writing automated tests to make sure your rust code works. There's lots of good books on rust, and I'd recommend checking them out.
  • You can build your own rust toolbox with these examples. Each exercise will have a title, an imaginary real world situation of where this could be useful. Feel free to use this code for whatever personal or commercial projects. I would love to have some other faces on the repo of people who have contributed.
  • Use rust argparse since we're building a command line tool. Take input from the user not through arguments, but by waiting. Create, read, update, and delete functions with the database. Have fun with these exercises.


This transcript was autogenerated. To make changes, submit a PR.
And welcome to Learning Rust by building CLI tools. Some intro about me could find me at Jim lynch codes, also in the New Jersey New York City area. Like to do lots of things. Been working as a software engineer for about ten years. I wouldn't consider myself a rust expert. Been coding in it for a few years, but sometimes still feel like I'm kind of a noob. And I would say my progression of my favorite programming languages started back with action Script, three flash games, and using Java for the back end and VBA for Microsoft applications. Then it kind of progressed to typescript, react and node js and all those kind of things. Got into clojure for a while, very functional lisp syntax, and now I feel like Rust is my favorite programming language. Kind of steals all these good things from the other ones. So why do people come to Rust? Well, it's probably faster than what you were using before, and it's also safer than C, C Plus plus, and less painful, dangerous to code in. There's no garbage collector virtual machine, and here is kind of a famous picture. This is from the blog posts of why discord is switching from go to rust. And you can see these spikes are basically the cpu working really hard, the response times taking a lot longer than they should. And this is pretty much from the garbage collector kicking in. Okay, so once people start using Rust, why do they end up falling in love with it? Usually the super elegant syntax, right? Just the fact that variables can never have a null value. You have this explicit syntax for all meetability fields, visibility heap for stack allocation, and it has a very functional ish feeling syntax, right? Just the match syntax and how if is an expression. Here's a chart that Rust developers love to show. This is the GitHub most loved programming languages, and we can see rust at the very top, number one by pretty large margin. Okay, so why use Rust for CLI tools? And why CLI tools as a way to learn Rust? Well, CLI tool is the default thing that's created when you run cargo new and create these new project. These CLi tools are usually small, isolated projects, which makes it easy to just practice one specific thing. Rust. And the speed and efficiency of rust make it a great choice for building a real CLI tool. One day you could use go or python or node js or something else, but even just that little bit of garbage collector virtual machine that has to boot up in the beginning, you'll usually find the split second of delay, and that can be annoying for some people. So it can be nice to build them in rust and then you just have everything execute extremely fast. But how do you know that it works? So you can use these small exercises as a way to practice not just writing the rust code to complete the task, but also to practice writing automated tests to make sure your rust code works. Okay, key thing is to put your unit tests and integration tests where cargo is expecting them. And here's a little example. Say we're testing this lib rs in the source folder. You'd put your implementation code for lib rs in that file, and you'd also put your unit tests for lib rs in that same file. Then in these integrationtest rs, you would put your integration tests and basically all the files inside of that tests folder that's parallel to source would hold all integration tests. Okay, you can also use these exercises as a way to get familiar with the macros used for testing, like these CFG test and assert books. Books are nice too. Here are a few books. There's lots of good books on rust, and I'd recommend checking them out. Reading them before, during after you're working through these exercises. The GitHub repo remember my handle is Jim lunchcodes. So they're at jimlenchcodes rust CLI exercises. And I also put together some example solutions. So these are my own personal solutions, not necessarily the only ones or the best ones, but you can find jimlinchcode rustclixamples and I just wanted to go over this real quick for people who are totally new to rust. Really awesome getting started with rust because we have rust up and you can find it at Rustsup Rs. Just one command works on Mac, windows and Linux, and it will install cargo, the compiler, everything you need for developing in rust. Okay, so with that out of the way, let's jump in and explore the exercises. Okay, so before we take a look at the code, just wanted to show you how to work on these projects. Okay, so we're here at the repository and I recommend making a fork of this. You can't push directly to my repository since you don't have permissions. I'm just going to choose one of my organizations here as these owner and you can copy the main branch only. That's fine. And the idea is that when you create a fork, this will copy all the files into a repo that you own. So then you can clone this, work through the projects, and push your solutions directly up to your repository here. Okay, here we are in vs code and I'm going to go through some of these files here. First, let's look at the readme in the root of this project. Okay? And this is saying again, we can use rest up to install cargo and everything. We can run cargo version to check that we have installed. And these, in each of these projects we can run the commands cargo run and cargo test. You can also run these tests with some code coverage output using this tarpaulin. And if you want to get crazy, you can even run mutation testing. Okay? And you can work through these in any order. They're totally independent. So the anatomy of an exercises. Each exercise will have a title, will have kind of a little backstory, an imaginary real world situation of where this could be useful. The exercise, the actual goal thing you need to accomplish some suggestions about how to write tests for this bullet points of the skills practice some things that you can add to your rust toolbox of just things that you're confident that you can do in rust. Bonus sometimes there will be bonus ideas for how you can push it further. And in a hints MD file, I've put some hints in case you get stuck. And just the idea of building your own rust toolbox where you have all these little examples of code that you've written. So if you need to do that again in the future, you have it right there in your toolbox as a reference or as code that you can just copy right over and allows you to just really hit the ground running. Okay, we talked about this a little bit. Why rust is great for CLI tools. Fast execution and startup time. Very low level control with these nice syntax. Cargo is a really awesome build tool and CLI tools just for working with rust. And coding with rust is know once you get the hang of it, you might find that you actually really like working in rust. And you really don't want to go back to coding in typescript or python or whatever you were doing before. Have the solutions these in these rust CLI examples. Repo contributing I would love to have some other faces on the repo of people who have contributed, maybe fixing typos or even adding more exercises here. Totally open to that. So open some issues if you have ideas or pull requests, if you want to just jump into working on it. And this is all MIT open source, so feel free to use this code for whatever personal or commercial projects that you have. Okay, now I'm just going to briefly talk about each of these projects. Hello world, the classic example. All you need to do is write a function that prints hello world bin files helps you to understand breaking up your functions into different files and modules and rust argparse since we're building a command line tool, you probably want to parse arguments. So that's positional arguments or flags that you can pass in either the long flag with two dashes or these short flag with one dash and these potentially taking arguments with your flags. For env reader, this is reading environment variables. If you have API keys or secrets, definitely recommended to save them into an environment variables file or somehow load them rather than just hard coding these into your code and pushing them up to get number five, table of chairs. This one, kind of goofy. We have a bunch of data about chairs and you want to render them in a table and this just helps you practice rendering a table of data in the command line. Number six, Fibonacci. In this one classic Fibonacci series, you're given a number and you want to return the Fibonacci series that ends with that. Number seven apology letter. This has some string parsing, some file loading read write. Basically you have an apology letter with some placeholders and you pass in the person's name and the thing you're apologizing for and we'll automatically generate an apology letter. Number eight, image resizer. This one you want to load an image and save that image in different sizes. Number nine GitHub scaffold. So in this one you're writing a CLI tool that automatically scaffolds a project from a repo on GitHub. So it's automatically doing that clone and pulling the files. Number ten, yes no. So in things one, you want to take input from the user not through arguments, but by waiting. It's kind of that give and take question sort of CLI tool where the program will run. It will ask you hey, we need an input, yes or no? And then the program will just sit there and hang until the user enters something, and then it will respond depending on if the user enters. Yes or no. Okay, number eleven, get json. This one is basically just making an API call, making a get rest call and parsing the jSon, displaying it. Okay, number twelve, happy birthday. This one has to do with working with dates. So basically you're given a birthday of the user and you need to display if it is the user's birthday or not, and if not, how many days until their next birthday. 13. Agile stand up. So in this one you're kind of just taking text input from the user. That has to do with agile stand up. So you're reading things like what did the person do yesterday, what did they work on, what are they working on today and if they are stuck on anything. 14. Pizza order so another one where you're taking text from the user. This one is about what type of pizza they would like, topping, size, and those kind of things. 15. Higher or lower? So this is sort of a guessing game where the program will think of a secret number and you have to guess between one and 100. And as you give wrong answers, it will tell you if the correct answer is higher or lower. 16. Wordle game so this one, no relation to New York Times or Josh Wordle or any of them, but this one is building a five letter word guessing game. Seventeen s these read, write. So this is reading and writing to an Amazon s three bucket. 18. Database crud so this one you are building. Create, read, update, and delete functions with the database. You have lots of freedom here to use any kind of database you would like. And I think it would be really interesting in my examples repo to have lots of different examples here of doing these crud operations with different databases. 19. Audio stutter so this one you're given can audio file and you need to make a cool stutter effect. And 20. Traveling salesman where you're given a graph of weighted edges and you have to write a function that finds these most efficient path. So that's all the exercises. Go through them. Have fun. Let me know if you get stuck. Thanks for watching my talk. Hope this was helpful and happy coding. Bye.

Jim Lynch

Software Engineer

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