Re: Proof of concept: Shepherd + DBus = ♥

["Ludovic Courtès" <ludo@gnu.org>]

Hello!

Liliana Marie Prikler <liliana.prikler@gmail.com> skribis:

> this comes a little late, as Gnome folks have decided that evaluating
> arbitrary Javascript over DBus is perhaps not always the wisest idea¹,

Too bad, what could possibly go wrong?

[...]

> Once you set the unsafe flag in Looking Glass and promise to be a very
> good girl, you can now extract environment variables.
>
> $ herd getenv gnome PATH              
>
> ;;; (reply #t "\"/gnu/store/s43dhx83c3a2g79vs5anf3wdmv9lwpi3-glib-
> 2.70.2-bin/bin:/run/setuid-
> programs:/home/yuri/.config/guix/current/bin:$HOME/.guix-
> profile/bin:$HOME/.guix-profile/sbin:/run/current-
> system/profile/bin:/run/current-system/profile/sbin\"")
>
>
> If you were naughty and didn't do the magic dance, you get a rather
> unhelpful result instead.
>
> $ herd getenv gnome PATH              
>
> ;;; (reply #f "")

This is super cool and super useful.  Is there some way we could achieve
this (getenv/setenv in the GNOME Shell process) without resorting to JS?

(💡 Did you know?  On GNU/Hurd, each process implements the “msg” RPC
interface, which, among other things, lets you inspect and change its
environment variables!  If you have a childhurd running, try something
like: “msgport --getenv=PATH -p $$”.)

> Anyway, we can now talk to DBus services from Shepherd, although doing
> so is currently a bit of a pain in the buttocks.  Much of this is due
> to guile-ac-d-bus being somewhat obtuse and not having enough fibers in
> it.  That being said, I'm sure there's some other use-case out there
> that is a good fit for this (wanna talk to loginctl for hibernation
> perhaps?)

Yes!  Provided suitable Fibers integration, we could have services that
automatically start/stop based on some notification received on the bus
(devices plugged/unplugged, power or network condition changes, etc.).
Pretty exciting.

Thanks for sharing!

Ludo’.