RubyGems ships with Ruby 1.9+. There is nothing to install. For prior versions of Ruby, see package instructions to install RubyGems.
Upgrade
To upgrade RubyGems.
gem update --system
Documentation
All gems have documentation that is generated when a gem is installed. To start the documentation web server.
gem server
To view the documentation, point your web browser to http://localhost:8808/.
Automatically Start the Documentation Server at Boot
Create a configuration file for Launchd.
nano ~/Library/LaunchAgents/org.rubygems.gem.plist
Copy and paste the following text into the aforementioned file. Make sure you update the path in the configuration below.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>org.rubygems.gem</string>
<key>ProgramArguments</key>
<array>
<string>/usr/local/ruby-*RUBY-VERSION*/bin/gem</string>
<string>server</string>
</array>
<key>StandardOutPath</key>
<string>/usr/local/var/log/rubygems.log</string>
<key>StandardErrorPath</key>
<string>/usr/local/var/log/rubygems.log</string>
<key>RunAtLoad</key>
<true/>
<key>KeepAlive</key>
<true/>
</dict>
</plist>
Register with Launchd and start the server.
launchctl load ~/Library/LaunchAgents/org.rubygems.gem.plist
Deregister with Launchd.
launchctl unload ~/Library/LaunchAgents/org.rubygems.gem.plist