rvm

TLDR

Install one or more versions of Ruby

$ rvm install [version1 version2 ...]

Display a list of installed versions

$ rvm list

Use a specific version of Ruby

$ rvm use [version]

Set the default Ruby version

$ rvm --default use [version]

Upgrade a version of Ruby to a new version

$ rvm upgrade [current_version] [new_version]

Uninstall a version of Ruby and keep its sources

$ rvm uninstall [version]

Remove a version of Ruby and its sources

$ rvm remove [version]

Show specific dependencies for your OS

$ rvm requirements