RubyGems User Guide
Publisher: RubyGems.org 2010
RubyGems is the premier ruby packaging system. It provides: A standard format for distributing Ruby programs and libraries; An easy to use tool for managing the installation of gem packages; A gem server utility for serving gems from any machine where RubyGems is installed; A standard way of publishing gem packages.
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This book is a great collection of ideas, tricks, and skills that could be useful for Hackers. It's a unique extraction reference, summarizes a lot of research and experience. Rubyfu is a book to use not only to read, it's where ruby goes evil.
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