Following the example from "pickaxe book", second edition, p128

#!/usr/bin/ruby 
File.open("testfile", "r") do |file|
  while line = file.gets
    puts line
  end
end

produces
copy.rb:2:in `initialize': No such file or directory - testfile (Errno::ENOENT)
        from copy.rb:2

-- 
John Maclean
MSc (DIC)
07739 171 531