Quickstart (require 'persistent-soft) (persistent-soft-store 'hundred 100 "mydatastore") (persistent-soft-fetch 'hundred "mydatastore") ; 100 (persistent-soft-fetch 'thousand "mydatastore") ; nil quit and restart Emacs (persistent-soft-fetch 'hundred "mydatastore") ; 100 Explanation This is a wrapper around pcache.el, providing "soft" fetch and store routines which never throw an error, but instead return nil on failure. There is no end-user interface for this library. It is only useful from other Lisp code. The following functions are provided: `persistent-soft-store' `persistent-soft-fetch' `persistent-soft-exists-p' `persistent-soft-flush' `persistent-soft-location-readable' `persistent-soft-location-destroy' To use persistent-soft, place the persistent-soft.el library somewhere Emacs can find it, and add the following to your ~/.emacs file: (require 'persistent-soft) See Also M-x customize-group RET persistent-soft RET Notes Using pcache with a more recent version of CEDET gives Unsafe call to `eieio-persistent-read'. eieio-persistent-read: Wrong type argument: class-p, nil This library provides something of a workaround. Compatibility and Requirements GNU Emacs version 24.4-devel : yes, at the time of writing GNU Emacs version 24.3 : yes GNU Emacs version 23.3 : yes GNU Emacs version 22.3 and lower : no Uses if present: pcache.el (all operations are noops when not present) Bugs Persistent-soft is a wrapper around pcache which is a wrapper around eieio. Therefore, persistent-soft should probably be rewritten to use eieio directly or recast as a patch to pcache. TODO Setting print-quoted doesn't seem to influence EIEIO. It doesn't seem right that the sanitization stuff is needed. Detect terminal type as returned by (selected-terminal) as unserializable. Correctly reconstitute cyclic list structures instead of breaking them. Notice and delete old data files. ; License Simplified BSD License: Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. This software is provided by Roland Walker "AS IS" and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. In no event shall Roland Walker or contributors be liable for any direct, indirect, incidental, special, exemplary, or consequential damages (including, but not limited to, procurement of substitute goods or services; loss of use, data, or profits; or business interruption) however caused and on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of this software, even if advised of the possibility of such damage. The views and conclusions contained in the software and documentation are those of the authors and should not be interpreted as representing official policies, either expressed or implied, of Roland Walker.