```ruby
require "uploadie/utils"

require "fileutils"
require "find"

class Uploadie
  module Storage
    class FileSystem
      attr_reader :directory, :subdirectory

      def initialize(directory, root: nil)
        if root
          @subdirectory = directory
          @directory = File.join(root, directory)
        else
          @directory = directory
        end

        FileUtils.mkdir_p(directory)
      end

      def upload(io, id)
        IO.copy_stream(io, path(id))
        io.rewind

        url(id)
      end

      def download(id)
        Uploadie::Utils.copy_to_tempfile(id, open(id))
      end

      def open(id)
        ::File.open(path(id), "rb")
      end

      def read(id)
        ::File.read(path(id))
      end

      def exists?(id)
        ::File.exist?(path(id))
      end

      def delete(id)
        FileUtils.rm(path(id))
      end

      def url(id)
        path(id)
      end

      def path(id)
        if subdirectory
          "/" + ::File.join(subdirectory, id)
        else
          ::File.join(directory, id)
        end
      end

      def clear!(confirm = nil, &condition)
        if condition
          Find.find(directory) do |path|
            condition.(path) ? FileUtils.rm(path) : Find.prune
          end
        else
          raise Uploadie::Confirm unless confirm == :confirm
          FileUtils.rm_rf(directory)
          FileUtils.mkdir_p(directory)
        end
      end
    end
  end
end
```

Add :host option to FileSystem storage for CDNs
user
```ruby
require "uploadie/utils"

require "fileutils"
require "find"

class Uploadie
  module Storage
    class FileSystem
      attr_reader :directory, :subdirectory, :host

      def initialize(directory, root: nil, host: "")
        if root
          @subdirectory = directory
          @directory = File.join(root, directory)
          @host = host
        else
          raise Error, ":host only works in combination with :root" if !host.empty?
          @directory = directory
        end

        FileUtils.mkdir_p(directory)
      end

      def upload(io, id)
        IO.copy_stream(io, path(id))
        io.rewind

        url(id)
      end

      def download(id)
        Uploadie::Utils.copy_to_tempfile(id, open(id))
      end

      def open(id)
        ::File.open(path(id), "rb")
      end

      def read(id)
        ::File.read(path(id))
      end

      def exists?(id)
        ::File.exist?(path(id))
      end

      def delete(id)
        FileUtils.rm(path(id))
      end

      def url(id)
        path(id)
      end

      def path(id)
        if subdirectory
          File.join(host, ::File.join(subdirectory, id))
        else
          ::File.join(directory, id)
        end
      end

      def clear!(confirm = nil, &condition)
        if condition
          Find.find(directory) do |path|
            condition.(path) ? FileUtils.rm(path) : Find.prune
          end
        else
          raise Uploadie::Confirm unless confirm == :confirm
          FileUtils.rm_rf(directory)
          FileUtils.mkdir_p(directory)
        end
      end
    end
  end
end
```
assistant