Someone
public text v1 · immutable[stijn@hermes ~]$ presbright=`cat /sys/class/backlight/sony/brightness`
[stijn@hermes ~]$ echo $presbright
6
[stijn@hermes ~]$ echo $(( ${presbright}-1 ))
5
[stijn@hermes ~]$ presbright=`cat /sys/class/backlight/sony/brightness`
[stijn@hermes ~]$ echo $presbright
6
[stijn@hermes ~]$ echo $(( ${presbright}-1 ))
5