Efficient Filesystem Handling

Various operating systems are willing to notify you of changes to files, but the API to register/receive updates varies (see rb-fsevent for OS X, rb-inotify for Linux, and rb-fchange for Windows). If you do not supply one of the supported gems for these methods, Guard will fall back to polling, and give you a warning about it doing so.

A challenge arises when trying to make these dependencies work with Bundler. If you simply put one of these dependencies into you Gemfile, even if it is conditional on a platform match, the platform-specific gem will end up in the Gemfile.lock, and developers will thrash the file back and forth.

There is a good solution. All three gems will successfully, quietly install on all three operating systems, and guard/listen will only pull in the one you need. This is a more proper Gemfile:

group :development do
  gem 'rb-inotify', :require => false
  gem 'rb-fsevent', :require => false
  gem 'rb-fchange', :require => false
end

If you're using Windows and at least Ruby 1.9.2, then Windows Directory Monitor is more efficient than using rb-fchange.