
  -spec get_cwd(Drive) -> {ok, Dir} | {error, Reason}
                   when
                       Drive :: string(),
                       Dir :: filename(),
                       Reason :: posix() | badarg.

  Returns {ok, Dir} or {error, Reason}, where Dir is the
  current working directory of the specified drive.

  Drive is to be of the form "Letter:", for example, "c:".

  Returns {error, enotsup} on platforms that have no concept of
  current drive (Unix, for example).

  Typical error reasons:

  enotsup:
    The operating system has no concept of drives.

  eacces:
    The drive does not exist.

  einval:
    The format of Drive is invalid.
