share emacs configuration between emacs 23 and emacs 24

Question

I'm trying to put all my emacs configuration under version control in order to easily switch between different computers. Actually my preferred system is OSX (10.8.3) with emacs 24.3 from http://emacsformacosx.com/. But I can also work in other systems (more likely linux-based although different distribution ubuntu/scientific-linux) which generally are equipped with emacs 23.4. What I would like to have is a init file which check the version of emacs and the operating system, load the needed packages from emacs package manager. So far my .emacs init file for emacs 24.3 on OSX is as follow

(require 'package)
(setq package-archives '(
    ("marmalade" . "http://marmalade-repo.org/packages/")
    ("org" . "http://orgmode.org/elpa/")
    ("melpa" . "http://melpa.milkbox.net/packages/")))
(package-initialize)

After that there are configuration (loaded separately as for example

(load "python-sy")

which uses some packages not installed as default: in particular

color-theme
org-mode
theme-changer
ess-site
magit
auctex
python.el (fgallina implementation)

plus some other things which relies in already built-in packages I admit that I have no idea on how to start for having a .emacs init file which could be used indifferently in all the devices. Furthermore I also would like to have a way to load url-proxy-services based on the system configuration

(setq url-proxy-services '(("http" . "proxy.server.com:8080")))

Thank you for any help

You can get a version of `package.el` for Emacs 23; follow the link on the [ELPA EmacsWiki page](http://www.emacswiki.org/emacs/ELPA). (Make sure to move it out of the way if/when the systems in question get upgraded to Emacs 24.) — legoscia, Jun 11 '13 at 14:13

giordano · Answer 1 · 2014-01-16T00:01:54.427

Relevant variables are system-type and emacs-major-version. You can use something like the following

(if (>= emacs-major-version 24)
    (progn
      ;; Do something for Emacs 24 or later
      )
  ;; Do something else for Emacs 23 or less
  )

(cond
 ((eq system-type 'windows-nt)
  ;; Do something on Windows NT
  )
 ((eq system-type 'darwind)
  ;; Do something on MAC OS
  )
 ((eq system-type 'gnu/linux)
  ;; Do something on GNU/Linux
  )
 ;; ...
 (t
  ;; Do something in any other case
  ))

score 1 · Answer 2 · answered Jun 11 '13 at 14:38

1

Along with giornado answer, you can also put your package-specific settings in a way they will be evaluated only when the package is present by testing the (require) result. Example with the bbdb package:

(when (require 'bbdb nil t)
    (progn ...put your (setq) and other stuff here... ))

answered Jun 11 '13 at 14:38

Seki

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Isn't `eval-after-load` better? That reduces slightly startup time and executes code only when necessary. – giordano Jun 11 '13 at 14:44
Dear Giordano can you make me an example of the use of eval-after-load ? – Nicola Vianello Jun 11 '13 at 14:52
2

@giordano: `eval-after-load` allow to execute code only if you load a package. In my example there are multiple packages that I want to load at startup, but without having an error if the packahe is not present (I used to share my `.emacs ` between a Linux, a Windows and a Mac hosts, and not all the same packages were installed in each). – Seki Jun 11 '13 at 14:58
1

@NicolaVianello: `eval-after-load` allows to execute code after a file has been loaded, not necessarily at startup. An example: `(eval-after-load "file" '(progn ....))`. What Seki suggests is slightly different: `(when (require ...) ...)` executes code always at startup. You can choose what fits your needs. – giordano Jun 11 '13 at 15:20

score 0 · Answer 3 · answered Oct 17 '13 at 07:38

For this situation I define few constants at the top of .emacs:

(defconst --xemacsp (featurep 'xemacs) "Is this XEmacs?")
(defconst --emacs24p (and (not --xemacsp) (>= emacs-major-version 24)))
(defconst --emacs23p (and (not --xemacsp) (>= emacs-major-version 23)))
(defconst --emacs22p (and (not --xemacsp) (>= emacs-major-version 22)))
(defconst --emacs21p (and (not --xemacsp) (>= emacs-major-version 21)))

Example usage:

(when --emacs24p
    (require 'epa-file)
    (epa-file-enable)
    (setq epa-file-cache-passphrase-for-symmetric-encryption t) ; default is nil
    )

Or:

  (if --emacs22p
      (c-toggle-auto-newline 1)
    (c-toggle-auto-state 1))

etc.

share emacs configuration between emacs 23 and emacs 24

3 Answers3