Hey, I'm a bit worried that this just delays potential errors until the corresponding value is used at some point down the line. If adding this, we should also handle the case that the input variables are nil.

I did this because on my computer one file does not exist :
ac_state = readfile(pre.."/AC/online")

I totally understand your point of view. I'll check to update this later.

I just amended my commit to add check on mandatory values

if a mandatory file is missing the function get_state return nil

i would add a popup/notiffication to inform that a file is missing but https://awesome.naquadah.org does not work any more and every thing i found need to require naughty, so i did not for now

This isn't satisfactory either: Assume one of the mandatory files is not found, then get_state returns nil and update crashes on the line text = percent .. "%", indiscriminately of which file wasn't found.

I think there are two options here:

1. crash immediately for missing "mandatory files" (using the readfile function as is) and only handle ac_state (+others?) differently with a checked function
2. try as best as we can, and leave out only missing information or in the display (or show, e.g. ???)

What do you prefer?

I amended my commit

in get_state() i checked values but never formated it
in uptdate() I formatted value with Err! if they can not be displayed

Great thanks.