The sys-uname library provides an interface for gathering information about your current platform. It allows retrieving information such as the OS name, OS version, system name, etc.

The Listen gem listens to file modifications and notifies you about the changes.

The ruby_parser (RP) package provides a Ruby parser written in pure Ruby. It outputs S-expressions which can be manipulated and converted back to Ruby via the ruby2ruby library.

This Ruby library provides an implementation of the Matrix and Vector classes. The Matrix class represents a mathematical matrix. It provides methods for creating matrices, operating on them arithmetically and algebraically, and determining their mathematical properties (trace, rank, inverse, determinant, eigensystem, etc.). The Vector class represents a mathematical vector, which is useful in its own right, and also constitutes a row or column of a Matrix.

Nokogiri (鋸) parses and searches XML/HTML, and features both CSS3 selector and XPath 1.0 support.

This Ruby module allows you to map simple HTML back into Markdown---e.g., if you want to import existing HTML data in your application.

Selenium implements the W3C WebDriver protocol to automate popular browsers. It aims to mimic the behaviour of a real user as it interacts with the application's HTML. It's primarily intended for web application testing, but any web-based task can be automated. This package provides the Ruby bindings of Selenium.

Connection_pool provides a generic connection pooling interface for Ruby programs.

The cane gem provides a great framework for running quality checks over your ruby project as part of continuous integration build. It comes with a few checks out of the box, but also provides an API for loading custom checks. This gem provides a set of additional checks.

Markaby allows writing HTML packages in pure Ruby. This is similar to the functionality provided by ERB, but without the mixture of HTML and additional ERB syntax.

This package implements a variant of Set whose elements are sorted in ascending order

Timers offers a collections of one-shot and periodic timers, intended for use with event loops such as async.

This library provides contracts for Ruby. A contract describes the correct inputs and output for a method, and will raise an error if a incorrect value is found.

Pseudo `IO` class from and to `String`.

Rack::Cache is suitable as a drop-in component to enable HTTP caching for Rack-based applications that produce freshness (Expires, Cache-Control) and/or validation (Last-Modified, ETag) information.

This package provides a collection of RuboCop cops to check for performance optimizations in Ruby code.

RubyRC4 is a pure Ruby implementation of the RC4 algorithm.

This package provides a collection of text algorithms: Levenshtein, Soundex, Metaphone, Double Metaphone, Porter Stemming.

Multihashes provides a simple, low-level multihash implementation for Ruby. A multihash is a digest with an embedded hash function code

Jekyll is a simple, blog aware, static site generator.

Slop provides a Ruby domain specific language for gathering options and parsing command line flags.

This gem implements bcrypt_pbkdf, which is a variant of PBKDF2 (Password-Based Key Derivation Function 2) with bcrypt-based pseudorandom function. This is currently used by net-ssh to read password encrypted Ed25519 keys.

Guard is a command line tool to easily handle events on file system modifications. Guard automates various tasks by running custom rules whenever file or directories are modified.

pkg-config can be used in your extconf.rb to properly detect need libraries for compiling Ruby native extensions.