rust/doc/tutorial-rustpkg.md

% Rust Packaging Tutorial

Introduction

Sharing is caring. Rust comes with a tool, rustpkg, which allows you to package up your Rust code and share it with other people. This tutorial will get you started on all of the concepts and commands you need to give the gift of Rust code to someone else.

Installing External Packages

First, let's try to use an external package somehow. I've made a sample package called hello to demonstrate how to do so. Here's how hello is used:

extern mod hello;

fn main() {
    hello::world();
}

Easy! But if you try to compile this, you'll get an error:

$ rustc main.rs 
main.rs:1:0: 1:17 error: can't find crate for `hello`
main.rs:1 extern mod hello;
          ^~~~~~~~~~~~~~~~~

This makes sense, as we haven't gotten it from anywhere yet! Luckily for us, rustpkg has an easy way to fetch others' code: the install command. It's used like this:

$ rustpkg install fragment

This will install a package named 'fragment' into your current Rust environment. I called it 'fragment' in this example because when using it with an external package like this, it's often a URI fragment. You see, Rust has no central authority for packages. You can build your own hello library if you want, and that's fine. We'd both host them in different places and different projects would rely on whichever version they preferred.

To install the hello library, simply run this in your terminal:

$ rustpkg install github.com/steveklabnik/hello

You should see a message that looks like this:

note: Installed package github.com/steveklabnik/hello-0.1 to /some/path/.rust

Now, compiling our example should work:

$ rustc main.rs
$ ./main 
Hello, world.

Simple! That's all it takes.

Workspaces

Before we can talk about how to make packages of your own, you have to understand the big concept with rustpkg: workspaces. A 'workspace' is simply a directory that has certain folders that rustpkg expects. Different Rust projects will go into different workspaces.

A workspace consists of any folder that has the following directories:

• src: The directory where all the source code goes.
• build: This directory contains all of the build output.
• lib: The directory where any libraries distributed with the package go.
• bin: This directory holds any binaries distributed with the package.

There are also default file names you'll want to follow as well:

• main.rs: A file that's going to become an executable.
• lib.rs: A file that's going to become a library.

Building your own Package

Now that you've got workspaces down, let's build your own copy of hello. Go to wherever you keep your personal projects, and let's make all of the directories we'll need. I'll refer to this personal project directory as ~/src for the rest of this tutorial.

Creating neccesary files

$ cd ~/src
$ mkdir -p hello/{src/hello,build,lib,bin}
$ cd hello

Easy enough! Let's do one or two more things that are nice to do:

$ git init .
$ cat > README.md
# hello

A simple package for Rust.

## Installation

```
$ rustpkg install github.com/YOUR_USERNAME/hello
```
^D
$ cat > .gitignore
.rust
build
^D
$ git commit -am "Initial commit."

If you're not familliar with the cat > idiom, it will make files with the text you type insie. Control-D (^D) ends the text for the file.

Anyway, we've got a README and a .gitignore. Let's talk about that .gitignore for a minute: we are ignoring two directories, build and .rust. build, as we discussed earlier, is for build artifacts, and we don't want to check those into a repository. .rust is a folder that rustpkg uses to keep track of its own settings, as well as the source code of any other external packages that this workspace uses. This is where that rustpkg install puts all of its files. Those are also not to go into our repository, so we ignore it all as well.

Next, let's add a source file:

#[link(name = "hello",
       vers = "0.1.0",
       uuid = "0028fbe0-1f1f-11e3-8224-0800200c9a66",
       url = "https://github.com/YOUR_USERNAME/hello")]; 

#[desc = "A hello world Rust package."];
#[license = "MIT"];
#[crate_type = "lib"];

pub fn world() {
    println("Hello, world.");
}

Put this into src/hello/lib.rs. Let's talk about each of these attributes:

Crate attributes for packages

crate_type is the simplest: we're building a library here, so we set it to "lib". If we were making an executable of some kind, we'd set this to "bin" instead.

license is equally simple: the license we want this code to have. I chose MIT here, but you should pick whatever license makes the most sense for you.

desc is a description of the package and what it does. This should just be a sentence or two.

link is the big complex attribute here. It's still not too complex: name is the name of the package, and vers is the version. If you're building a library, consider using Semantic Versioning as your versioning scheme. Future versions of rustpkg will assume SemVer.

uuid is simply a unique identifier. You can generate a UUID by visiting this page. Just copy whatever it puts out into the value for uuid. For more on UUIDs, see RFC4122.

Finally, url is a URL where this package is located. Easy.

Building your package

Building your package is simple:

$ rustpkg build hello

This will compile src/hello/lib.rs into a library. After this process completes, you'll want to check out build:

$ ls build/x86_64-unknown-linux-gnu/hello/
libhello-ed8619dad9ce7d58-0.1.0.so

This directory naming structure is called a 'build triple,' and is because I'm on 64 bit Linux. Yours may differ based on platform.

You'll also notice that src/hello/lib.rs turned into libhello-ed8619dad9ce7d58-0.1.0.so. This is a simple combination of the library name, a hash of its content, and the version.

Now that your library builds, you'll want to commit:

$ git add src
$ git commit -m "Adding source code."

If you're using GitHub, after creating the project, do this:

$ git remote add origin git@github.com:YOUR_USERNAME/hello.git
$ git push origin -u master

Now you can install and use it! Go anywhere else in your filesystem:

$ cd ~/src/foo
$ rustpkg install github/YOUR_USERNAME/hello
WARNING: The Rust package manager is experimental and may be unstable
note: Installed package github.com/YOUR_USERNAME/hello-0.1 to /home/yourusername/src/hello/.rust

That's it!

More resources

There's a lot more going on with rustpkg, this is just to get you started. Check out the rustpkg manual for the full details on how to customize rustpkg.

A tag was created on GitHub specifically for rustpkg-related issues. You can see all the Issues for rustpkg here, with bugs as well as new feature plans. rustpkg is still under development, and so may be a bit flaky at the moment.

You may also want to check out this blog post, which contains some of the early design decisions and justifications.