Get the tty attributes for file descriptor fd.
Returns a list [iflag, oflag, cflag, lflag, ispeed, ospeed, cc]
where cc is a list of the tty special characters (each a string of
length 1, except the items with indices VMIN and VTIME, which are
integers when these fields are defined). The interpretation of the
flags and the speeds as well as the indexing in the cc array must be
done using the symbolic constants defined in this module.