--- /dev/null
+## Copyright (C) 2004-2012 Alois Schloegl
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING. If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} isdir (@var{f})
+## Return true if @var{f} is a directory.
+## @seealso{is_absolute_filename, is_rooted_relative_filename}
+## @end deftypefn
+
+function retval = isdir (f)
+ if (nargin != 1)
+ print_usage ("isdir");
+ endif
+
+ ## Exist returns an integer but isdir should return a logical.
+ retval = (exist (f, "dir") == 7);
+
+endfunction
+
+%!error isdir ();
+%!error isdir (1, 2);
+
+%!assert (isdir (pwd ()));
+%!assert (! isdir ("this is highly unlikely to be a directory name"));