How to check for downloads to complete and get the file name

watir-webdriver-downloads.rb

require 'watir-webdriver'

file_name = nil
download_directory = "#{Dir.pwd}/downloads"
download_directory.gsub!("/", "\\") if Selenium::WebDriver::Platform.windows?
downloads_before = Dir.entries download_directory
 
profile = Selenium::WebDriver::Firefox::Profile.new
profile['browser.download.folderList'] = 2 # custom location
profile['browser.download.dir'] = download_directory
profile['browser.helperApps.neverAsk.saveToDisk'] = "text/csv,application/pdf"
 
b = Watir::Browser.new :firefox, :profile => profile

b.goto 'https://dl.dropbox.com/u/18859962/hello.csv'

30.times do
  difference = Dir.entries(download_directory) - downloads_before
  if difference.size == 1
		file_name = difference.first 
    break
  end  
  sleep 1
end
raise "Could not locate a new file in the directory '#{download_directory}' within 30 seconds" if not file_name
puts file_name