Per-host background colour

Question

Having got a bunch of custom colors defined (thanks to Drew), I need to use them to customize the background color per host. I have named the colors after the hostname, eg

(setq pentacle "#314159")
(setq athame "#271828")

so then I tried (at the bottom of the .emacs file)

(set-background-color (nth 0 (split-string (system-name) "\\.")))

but on (for example) pentacle.mydomain.com I get the message in the minibuffer

Undefined color: "pentacle"

I assume I need one or more additional levels of indirection in expanding the system name and splitting off the first token from the FQDN, but I can't see how to do this so that it gets recognized as the variable I defined.

Answer 1

The path you have chosen introducing symbols to keep the colors requires you to convert the names you get by system-name to those symbols and evaluate them to get the color.

You could achieve this by

(set-background-color
 (symbol-value (intern (nth 0 (split-string (system-name) "\\.")))))

Although doable I think the above is rather unconventional.

A more conventional approach would keep the mapping of machine names to colors in a structure like an association list.

Your example could be implemented as follows.

(setq colors-for-machines
      '(("pentacle" . "#314159")
        ("athame" . "#271828")))

Retrieve the right value:

(set-background-color
 (cdr
  (assoc (nth 0 (split-string (system-name) "\\."))
         colors-for-machines)))