~/bin/gemdir

gemdir.rb

#! /usr/bin/env ruby
 
# usage: gemdir gemname
#
# eg: cd `gemdir yajl`
#
require 'rubygems'

arg = ARGV.first

unless arg
  puts File.join(Gem.dir, "gems")
  exit
end

which = arg.dup
which << '*' if which

entries =
  Dir[ File.join(Gem.dir, "gems", "#{ which }") ].select{|entry| test ?d, entry}.sort

case entries.size
  when 0
    abort "no gem #{ which }"

  when 1
    puts entries.first

  else
    all_same_name = entries.map{|e| File.basename(e).split('-').first}.uniq.size == 1

    if all_same_name
      puts entries.last
    else
      unless STDIN.tty?
        warn "ambiguous gemname #{ arg.inspect }"
      end
      abort(entries.join("\n"))
    end
end