Automatic Library Reloading


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Autoreload automatically reloads library files after they have been updated. It is especially useful when testing stateless services such as web applications.

IMPORTANT! Version 1.0+ has a new API. It also works best under Ruby 1.9 or above. Under Ruby 1.8 or older files are reloaded regardless of whether they actually have changed since the last load. Whereas in Ruby 1.9+, they only reload if the mtime on the file is newer than the previous time.


Say we have a library foo.rb in our load path:

def foo

We can then run the following script, example.rb:

require 'autoreload'

autoreload(:interval=>2, :verbose=>true) do
  require 'foo.rb'

loop {
  puts foo
  sleep 2

While that's running we can change foo.rb and the change will take effect in example.rb within two seconds of being made.

Note that autoreload only works with required files. It cannot monitor files that are brought in with #load. This is because $LOADED_FEATURES is used to track which files are monitored.


The current version of Autoreload is a derviative of Kouichirou Eto's original work which can still be found at

License & Copyrights

Autoreload is released as free software under the BSD-2-Clause license.

  • Copyright 2010 Rubyworks
  • Copyright 2003 Kouichirou Eto

See for details.