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.
gem command [arguments...] [options...]
gem install rake
gem list --local
gem build package.gemspec
gem help install
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
with info about installed gems
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.