Ruby

Ruby is a dynamic, interpreted, open source programming language with a focus on simplicity and productivity.

Installing Ruby

The version of Ruby you need to install depends on your requirements. If you are supporting a legacy application, install Ruby 1.9 or 1.8 as necessary. If you are starting a new project, Ruby 2.0 is recommended. Below is a summary of the available versions and how to get them.

Ruby 2.0

To install Ruby 2.0.0, install ruby. Ruby 2.0 includes RubyGems.

Ruby 1.9

To install Ruby 1.9, install ruby1.9^AUR from the AUR. Ruby 1.9 includes RubyGems.

Ruby 1.8

To install Ruby 1.8, install ruby1.8^AUR from the AUR. Ruby 1.8 does not include RubyGems. Instead, it is available through the rubygems1.8^AUR package.

Multiple versions

If you want to run multiple versions on the same system (e.g. 2.0.0-p0 and 1.9.3-p392), the easiest way is to use RVM or rbenv.

Documentation

To make documentation available through the included ri command-line tool, install ruby-docs. You can then query the docs with: ri Array, ri Array.pop etc. (much like man-pages)

RubyGems

gem is a package manager for Ruby modules (called Gems), somewhat comparable to what pacman is to Arch Linux. The gem command will be installed if you followed the installation instructions above.

Usage

To see what gems are installed:

$ gem list

To get information about a gem:

$ gem spec gem_name

By default, gem list and gem spec use the --local option, which forces gem to search only the local system. This can be overridden with the --remote flag. Thus, to search for the mysql gem:

$ gem list --remote mysql

To install a gem:

$ gem install mysql

The process can be sped up somewhat if you do not need local documentation:

$ gem install mysql --no-rdoc --no-ri

To update all installed gems:

$ gem update

Running as normal user

When running gem as a normal user, gems are installed into ~/.gem instead of system-wide. This is considered the best way to manage gems on Arch. Unfortunately, not all gems are happy with being installed in this way, and might insist on being installed by root, especially if they have native extensions (compiled C code). This per-user behavior is enabled via /etc/gemrc and can be overridden by a ~/.gemrc file.

To use gems which install binaries, you need to add ~/.gem/ruby/2.0.0/bin to your $PATH.

Running as root

When running as root, the gems will be installed into /root/.gems and will not be installed to /usr/lib/ruby/gems/.

Note: See bug #33327 for more information.

Bundler solves these problems to some extent by packaging gems into your application. See the section below on using bundler.

Bundler

Bundler allows you to specify which gems your application depends upon, and optionally which version those gems should be. Once this specification is in place, Bundler installs all required gems (including the full gem dependency tree) and logs the results for later inspection. By default, Bundler installs gems into a shared location, but they can also be installed directly into your application. When your application is run, Bundler provides the correct version of each gem, even if multiple versions of each gem have been installed. This requires a little bit of work: applications should be called with bundle exec, and two lines of boilerplate code must be placed in your application's main executable.

To install Bundler:

$ gem install bundler

By default, Bundler installs gems system-wide, which is contrary to the behaviour of gem itself on Arch. To correct this, add the following to your ~/.bashrc:

export GEM_HOME=~/.gem/ruby/2.0.0

To start a new bundle:

$ bundle init

Then edit Gemfile in the current directory (created by bundle init) and list your required gems:

Gemfile

gem "rails", "3.2.9"
gem "mysql"

Run the following to install gems into GEM_HOME:

$ bundle install

Alternatively, run the following to install gems to .bundle in the working directory:

$ bundle install --path .bundle

Don't forget to edit your main executable:

#!/usr/bin/env ruby

# "This will automatically discover your Gemfile, and make all of the gems in
# your Gemfile available to Ruby." http://gembundler.com/v1.3/rationale.html
require 'rubygems'
require 'bundler/setup'

...

Finally, run your program:

bundle exec main_executable_name.rb

Managing RubyGems using pacman

Instead of managing gems with gem, you can use pacman, or some AUR helper. Ruby packages follow the naming convention ruby-[gemname]. This option provides the following advantages:

• Gems are updated along with the rest of your system. As a result, you never need to run gem update: # pacman -Syu suffices.
• Installed gems are available system-wide, instead of being available only to the user who installed them.

If a gem is not available in the repositories, you can use pacgem^AUR to automatically create a package, which can then be installed by pacman.

See also

• Ruby On Rails
• Ruby - http://ruby-lang.org/
• Rubyforge - http://rubyforge.org
• Bundler - http://github.com/carlhuda/bundler