Ruby and Rails FAQ(s)

Knowing these stuff will be handy when in need and so do I post them here. If you think of (m)any stuff that should be helpful please do add them/it through comments to this post and I shall add them/it to my list of FAQs sooner.

1. How to find the current version of Ruby installed?
   $ruby -v or  
   $ruby --version
2. How to find the current version of RubyGem installed?
   $gem -v or  
   $gem --version
3. How to find the current version of Rails installed?
   $rails -v or  
   $rails --version
4. How to find environment information of RubyGems?
   $gem env
5. How to update the current version of Rails installed?
   $sudo gem update rails
6. How to install rails and its dependencies?
   $sudo gem install rails --include-dependencies
7. How to find the list of plugins installed as part of gem in use?
   $gem list --local
8. [More to come...]

Books I follow(ed) for Ruby are:

   

Books I follow(ed) for Rails: