##
  # Select() examines the I/O descriptor sets who are passed in
  # +read_array+, +write_array+, and +error_array+ to see if some of their descriptors are
  # ready for reading, are ready for writing, or have an exceptions pending.
  #
  # If +timeout+ is not nil, it specifies a maximum interval to wait
  # for the selection to complete. If timeout is nil, the select
  # blocks indefinitely.
  # 
  # +write_array+, +error_array+, and +timeout+ may be left as nil if they are
  # unimportant