check which version of rubygems installed on ubuntu?

How do I check which version of rubygems i have installed on my ubuntu box?

From serverfault John

• Just an idea, list the installed packages and grep for ruby or gems or whatever :)

  dpkg --get-selections

  ptman : Wouldn't it be better to ask for a specific package? Like `dpkg -l rubygems`

  Marcel : What if you don't know the package name ? does this work : dpkg -l \*ruby\* ?
  From Marcel

• Either gem -v or gem --version would output the version number.

  For more information:

  $ gem -h
  RubyGems is a sophisticated package manager for Ruby.  This is a
  basic help message containing pointers to more information.
  
    Usage:
      gem -h/--help
      gem -v/--version
      gem command [arguments...] [options...]
  
    Examples:
      gem install rake
      gem list --local
      gem build package.gemspec
      gem help install
  
    Further help:
      gem help commands            list all 'gem' commands
      gem help examples            show some examples of usage
      gem help platforms           show information about platforms
      gem help <COMMAND>           show help on COMMAND
                                     (e.g. 'gem help install')
      gem server                   present a web page at
                                   http://localhost:8808/
                                   with info about installed gems
    Further information:
      http://rubygems.rubyforge.org
  

  I've seen on another question that you have the gem app broken. And that you have updated it with gem update --system. If this is the case, you can look on /usr/lib/ruby/gems/1.8/gems/rubygems-update-x.x.x and take the directory with the highest value of x.x.x.

  From chmeee