remove_old_gems.rb

#!/bin/env ruby

rbgem = `which gem`.strip
output = `#{rbgem} list --local`

output.each do |line|
  matches = line.match(/([A-Z].+) \(([0-9\., ]+)\)/i)
  if matches
    gem_name = matches[1]
    versions = matches[2].split(', ')[1..-1]
    versions.each do |ver|
      cmd = "#{rbgem} uninstall #{gem_name} -i -v #{ver}"
      puts "#{gem_name}-#{ver}"
      system cmd
    end
  end
end

puts "Uninstalled all old gems!" if output !=~ /,/