read_proc.rb

class IO
    def read
    if @eof
      ''
    else
      `res = self.read_proc(@path)`
      @eof = true
      @lineno = res.size
      res
    end
  end
end

FILE_READER = IO.new

def file_read(path)
  File.read(@path)
end
FILE_READER.read_proc = file_read

FILE_READER.extend(IO::Readable)