Using JS to write to file under /sys

[Alessandro Crismani <alessandro crismani gmail com>]

Hi there,

I do not know if this list is the right ML for this question, but I do 
not know where exactly it should go. Suggestions are welcomed if I am 
out of scope.

I am trying to write a GJS program (which at some point I might turn 
into a Gnome Shell extension) that modifies files under /sys. 
Particularly, I want to write 0 or 1 into some files that regulate the 
behaviour of my Samsung laptop's battery life extender technology, 
silent mode and other stuff. These file are under 
/sys/devices/platform/samsung and hence require root access. Here come 
the questions:

1) Which is the best way to grant root privileges to such a program? I 
though about using policykit, but I didn't find much about it when 
combined with GJS. Does anybody have a stupid example on how to give 
permission to write to such a file to a GJS program? Do I have to run 
the program as pkexec program.js, or can I just execute some of its 
parts with higher privileges?

2) I tried avoiding the permission thing by running the program as root, 
for seeing whether it was working or not. It seems that my way of 
writing to a file fails even if I have proper permissions (root can echo 
to such file). What I tried is:

	const batteryFile = "/sys/devices/platform/samsung/battery_life_extender";
	GLib.file_set_contents(batteryFile, "1");

but I get an error that sounds like:

root at alessandro-sammy in /data/Documenti/Linux/SammySettings
# LC_ALL=C gjs SammySettings.js
	JS ERROR: !!!   Exception was: Error: Error invoking 
GLib.file_set_contents: Failed to create file 
'/sys/devices/platform/samsung/battery_life_extender.ZTDFIW': No such 
file or directory
	JS ERROR: !!!     lineNumber = '0'
	JS ERROR: !!!     fileName = '"gjs_throw"'
	JS ERROR: !!!     stack = '"("Error invoking GLib.file_set_contents: 
Failed to create file 
'/sys/devices/platform/samsung/battery_life_extender.ZTDFIW': No such 
file or directory")@gjs_throw:0
([object _private_Gtk_Switch],[object 
_private_GObject_ParamSpec])@SammySettings.js:108
wrapper([object _private_Gtk_Switch],[object 
_private_GObject_ParamSpec])@/usr/share/gjs-1.0/lang.js:204
@SammySettings.js:146
"'
	JS ERROR: !!!     message = '"Error invoking GLib.file_set_contents: 
Failed to create file 
'/sys/devices/platform/samsung/battery_life_extender.ZTDFIW': No such 
file or directory"'

What am I missing? Which is *the* way for modifying such root owned 
files (without changing their ownership, obviously)?

Thanks a lot, and sorry if these questions sound stupid, but I am really 
new to this kind of things and I do not know where to search/ask.

Cheers,
Alessandro