title: Chef Recipes, not_if
body: <p>bash "edit gemfile" do</p>
  
  <pre><code>cwd "/home/vagrant/myapp"
  code &lt;&lt;-EOH
  echo "group :development, :test do
  gem 'capybara'
  gem 'rspec-rails'
  gem 'selenium-webdriver'
  gem 'capybara-screenshot'
  gem 'launchy'
  end" &gt;&gt;Gemfile
  EOH
  #####not_if do ::File.exists?('/home/vagrant/myapp/Gemfile') end#####
  end
  </code></pre>
  
  <p>I want it to not add it again on Gemfile once it is added already to avoid duplicate...
  please tell me how to use the proper not_if command, thanks!</p>