Gemfile

Gemfile

source 'http://rubygems.org'

# default group
gem "json"

# for mac os
group :darwin do
  gem 'rb-fsevent'
  gem 'growl'
end

# for linux
group :linux do
  gem "arel"
end

group :dev do
  gem "active_support"
end

platforms :ruby do
  gem "hpricot"
end

platforms :jruby do
  gem "nokogiri"
end

=begin
hooopo@hooopo:~/rails3/bundler$ bundle install --without darwin
Fetching source index for http://rubygems.org/
Using activesupport (3.0.0) 
Using active_support (3.0.0) 
Using arel (2.2.1) 
Using hpricot (0.8.4) 
Using json (1.6.1) 
Using bundler (1.0.13) 
Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.
hooopo@hooopo:~/rails3/bundler$ cat Gemfile.lock 
GEM
  remote: http://rubygems.org/
  specs:
    active_support (3.0.0)
      activesupport (= 3.0.0)
    activesupport (3.0.0)
    arel (2.2.1)
    growl (1.0.3)
    hpricot (0.8.4)
    json (1.6.1)
    rb-fsevent (0.4.3.1)

PLATFORMS
  ruby

DEPENDENCIES
  active_support
  arel
  growl
  hpricot
  json
  nokogiri
  rb-fsevent
=end