Subject: acpi scripts have started inserting '?' in console

From: "Paul W. Rankin" <[email-masked]>
Date: Fri, 25 Nov 2022 17:53:34 +1000

Hello,

I have the following acpi scripts:

$ cat /etc/acpi/brightness-up
#!/bin/sh
read brightness < /sys/class/backlight/edp-backlight/brightness
read max < /sys/class/backlight/edp-backlight/max_brightness
inc=256
target=$(( brightness + inc ))

echo $(( target < max ? target : max )) > 
/sys/class/backlight/edp-backlight/brightness
$ cat /etc/acpi/brightness-down
#!/bin/sh
read brightness < /sys/class/backlight/edp-backlight/brightness
inc=256
target=$(( brightness - inc ))

echo $(( 0 < target ? target : 0 )) > 
/sys/class/backlight/edp-backlight/brightness

These work to increase/decrease the screen brightness, but recently (not 
sure how recent) they have started to insert '?' at the console (not X). 
This doesn't appear to be a real character, because I can, e.g.

$ ????echo 0
0

Any idea what's wrong with my implementation?

Thanks