Re: Persistence of variables

[Marcin Borkowski <mbork@mbork.pl>]

On 2018-03-21, at 08:25, Marcin Borkowski <mbork@mbork.pl> wrote:

> On 2018-03-21, at 07:55, Eli Zaretskii <eliz@gnu.org> wrote:
>
>>> From: Marcin Borkowski <mbork@mbork.pl>
>>> Date: Wed, 21 Mar 2018 07:08:44 +0100
>>> 
>>> I want to make a variable persistent across Emacs sessions.  How do I do
>>> it?
>>
>> Did you consider desktop.el?
>
> No, I did not remember about its existence.
>
> But no, way too heavy.  I want _one variable_ to persist, and nothing
> more.

OK, how about this?

--8<---------------cut here---------------start------------->8---
(defun make-variable-persistent (variable-name)
  "Save VARIABLE-NAME to `custom-file' or `init-file'."
  (when (y-or-n-p (format "I am going to save variable `%s' in %s.  Should I proceed? " variable-name user-init-file))
    (with-temp-file user-init-file
      (let ((sentinel-text (format "\n;; Persistent variable `%s'.  Do not edit manually!\n" variable-name)))
	(insert-file-contents user-init-file)
	(if (search-forward sentinel-text nil t)
	    (if (not (looking-at-p (format "^(setq %s" variable-name)))
		(error "Broken init file.")
	      (kill-sexp))
	  (goto-char (point-max))
	  (insert sentinel-text)))
      (insert (format "(setq %s %S)" variable-name (symbol-value variable-name))))))
--8<---------------cut here---------------end--------------->8---

Any thoughts/suggestions?

-- 
Marcin Borkowski
http://mbork.pl