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@pcting
Last active July 29, 2022 22:57
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backlight script for Lenovo ThinkPad P15s Gen 2i
#!/bin/bash
# Example: increae brightness by 15%
# backlight.sh inc 15
CURRENT_BRIGHTNESS=$(cat /sys/class/backlight/intel_backlight/brightness)
MAX_BRIGHTNESS=$(cat /sys/class/backlight/intel_backlight/max_brightness)
ONE_PERCENT_FACTOR=$(( MAX_BRIGHTNESS / 100 ))
BRIGHTNESS_STEP=$2
case "$1" in
-inc )
NEW_BRIGHTNESS=$(( CURRENT_BRIGHTNESS + (BRIGHTNESS_STEP * ONE_PERCENT_FACTOR) ))
;;
-dec )
NEW_BRIGHTNESS=$(( CURRENT_BRIGHTNESS - (BRIGHTNESS_STEP * ONE_PERCENT_FACTOR) ))
;;
*)
echo $CURRENT_BRIGHTNESS ' / ' $MAX_BRIGHTNESS
exit 0
;;
esac
NEW_BRIGHTNESS=$((NEW_BRIGHTNESS>MAX_BRIGHTNESS ? MAX_BRIGHTNESS : NEW_BRIGHTNESS))
NEW_BRIGHTNESS=$((NEW_BRIGHTNESS<0 ? 0 : NEW_BRIGHTNESS))
# need permissions to write:
# $ cat /etc/sudoers.d/intel_backlight
# ALL ALL = (ALL) NOPASSWD: /usr/bin/tee /sys/class/backlight/intel_backlight/brightness
echo $NEW_BRIGHTNESS | sudo tee /sys/class/backlight/intel_backlight/brightness
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