A native extension exposing the OS X FSEvents API. RubyCocoa not required.
Ruby C
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A native extension exposing the OS X FSEvent API.

Register the directories you want to watch, create a custom callback, and your callback will fire everytime a change occurs in the registered directories.


class PrintChange < FSEvent
  def on_change(directories)
    puts "Detected change in: #{directories.inspect}"

printer = PrintChange.new
printer.watch_directories %W(#{Dir.pwd} /tmp)

Examine ruby-fsevent/examples

  1. rake make
  2. ruby examples/print_changes.rb
  3. Notice that the examples directory and the /tmp directory are being monitored
  4. Make a change to either directory and watch the callback fire


  • Documentation
  • Add ability to register a block as a callback handler, on_change would then call the block. This removes the need for subclassing.
  • Expose an optional ruby library to show file changes, not just directory changes
  • Do more in Ruby, less in C


I'm tired of recompiling RubyCocoa just get Rspactor working whenever I switch Ruby versions. Hopefully, this gem will break that dependency.

Watchr and Kicker have recently grabbed my attention. They allow you to watch directories for changes and create custom event handlers. Unfortunately, Watchr has a 4-5 second delay when using it with Rev (recommended) before your callback is fires. Without Rev, Watchr degrades to a 0.5 second Ruby loop which we all know is not resource-friendly. Now, Watchr could easily add native FSEvents as a new backend for Mac users.

Kicker already uses the FSEvents API but it requires RubyCocoa just like Rspactor. They could easily switch their dependency to this native extension and remove the need for RubyCocoa.

With a generic, native interface to the FSEvent API we, as Rubyists can harness the power of OSX FSEvents without depending on RubyCocoa.

Note on Patches/Pull Requests

  • Fork the project.
  • Make your feature addition or bug fix.
  • Add tests for it. This is important so I don't break it in a future version unintentionally.
  • Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
  • Send me a pull request. Bonus points for topic branches.


Copyright (c) 2009 Sandro Turriate. See LICENSE for details.