Updated to use newer ack. Only outputs the filenames. You can use: $ rake find_unused_images > unused_images.txt $ xargs rm < ./unused_images.txt to delete them all! Also, supports multiple directories.. and filenames are shellescaped.

find_unused_images.rake

# It requires ACK - http://betterthangrep.com/
# Modified from https://gist.github.com/rafaelp/4467738
# Please add the following filetypes to your .ackrc
# --type-set=haml=.haml
# --type-set=sass=.sass
# --type-set=scss=.scss
# --type-set=erb=.erb
# --type-set=coffee=.coffee
# Based on: https://github.com/docwhat/homedir-examples/pull/3
task :find_unused_images do
  # Look in two folders by default.
  directories = [
    'app/assets/images/**/*', 
    'public/images/**/*'
  ]
  #puts "=======================\nDelete unused files below:"
  directories.each do |path|
    images = Dir.glob(path)
    images.each do |image|
      unless File.directory?(image)
        result = `ack -1 --ignore-directory=tmp --ignore-directory=log --ruby --html --css --js --sass --scss --coffee --erb --haml #{File.basename(image).shellescape}`
        if result.empty?
          print "./" + image.shellescape + "\n"
        end
      end #unless File.directory?(image)
    end #images.each
  end #directories.each
end #task