Adjust backlight throughout the day to correspond to the location of the sun

autobacklight

#!/bin/bash
# /usr/local/bin/autobacklight

BL_DARK=15
BL_BRIGHT=187
SOLAR_NOON=17:15Z


now_s=$(date +%s)
noon_s=$(date -d "${SOLAR_NOON}" +%s)
bl_t=$(bc -l <<MATH
  pi = 3.14159;
  blm = (${BL_BRIGHT} - ${BL_DARK})/2;
  blz = ${BL_DARK};
  rad = (1 + c((${now_s} - ${noon_s})/(12*60*60)*pi));
  rad * blm + blz

MATH
)
bl_tr=$(printf "%.0f\n" "${bl_t}")

bl_current=$(cat /sys/class/backlight/intel_backlight/brightness)

if [ "$bl_current" -gt "$bl_tr" ]; then
  echo $(($bl_current - 1)) > /sys/class/backlight/intel_backlight/brightness
fi
if [ "$bl_current" -lt "$bl_tr" ]; then
  echo $(($bl_current + 1)) > /sys/class/backlight/intel_backlight/brightness
fi

autobacklight-first-run.service

# /etc/systemd/system/autobacklight-first-run.service
# systemctl enable autobacklight-first-run.service

[Unit]
Description=where's the sun?
Before=sysinit.target shutdown.target

[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/usr/local/bin/autobacklight_first_run

[Install]
WantedBy=multi-user.target

autobacklight.service

[Unit]
Description=Adjust backlight corresponding to position of the sun

[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/usr/local/bin/autobacklight
ExecReload=/usr/local/bin/autobacklight
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target

autobacklight.timer

# /etc/systemd/system/autobacklight.timer
# systemctl enable autobacklight.timer

[Unit]
Description=Adjusts backlight to correspond to the position of the sun


[Timer]
OnUnitActiveSec=5s
OnActiveSec=60s
Unit=autobacklight.service

[Install]
WantedBy=multi-user.target

autobacklight_first_run

#!/bin/bash
# /usr/local/bin/autobacklight_first_run
  
BL_DARK=15
BL_BRIGHT=187
SOLAR_NOON="17:15Z"
DEV="/sys/class/backlight/intel_backlight/brightness"

now_s=$(date +%s)
noon_s=$(date -d "${SOLAR_NOON}" +%s)
bl_t=$(bc -l <<MATH
  pi = 3.14159;
  blm = (${BL_BRIGHT} - ${BL_DARK})/2;
  blz = ${BL_DARK};
  rad = (1 + c((${now_s} - ${noon_s})/(12*60*60)*pi));
  rad * blm + blz

MATH
)
bl_tr=$(printf "%.0f\n" "${bl_t}")

echo $bl_tr > "$DEV"