5 POSIX specification: @url{http://www.opengroup.org/onlinepubs/9699919799/functions/rmdir.html}
9 Portability problems fixed by Gnulib:
12 This function is missing on some old platforms.
15 Portability problems not fixed by Gnulib:
18 When @code{rmdir} fails because the specified directory is not empty, the
19 @code{errno} value is system dependent.