Battery level checking service

battery-level-check.service

#
# Save this file as: /etc/systemd/system/battery-level-check.service
#

[Unit]
Description=Battery check. If higher than 80% or lower than 40%, notify desktop user
Wants=battery-level-check.timer

[Service]
Type=simple
ExecStart=/usr/local/bin/battery-level-check

[Install]
WantedBy=graphical.target

battery-level-check.sh

#!/bin/bash

#
# Save this file as: /usr/local/bin/battery-level-check
#

function notify_user {
	DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS sudo -u $DESKTOP_USER -E notify-send \
		--urgency=critical \
		$@
}

IFS=\0

# Assuming the system has tty2 dedicated for desktop user
DESKTOP_USER=$(who | grep tty2 | cut -d' ' -f1)
if [ "$DESKTOP_USER" == "" ]; then
	# no active desktop user
	exit 0
fi

# Gather desktop user and power information
DESKTOP_UID=$(id -u "$DESKTOP_USER")
DBUS_SESSION_BUS_ADDRESS="unix:path=/run/user/$DESKTOP_UID/bus"
POWER=$(upower -i /org/freedesktop/UPower/devices/battery_BAT0 | grep percentage | cut -d':' -f2 | sed 's/^[[:blank:]]*//;s/[[:blank:]]*$//')
POWER_NUM=${POWER%\%}
BATTERY_STATE=$(upower -i /org/freedesktop/UPower/devices/battery_BAT0 | grep state | cut -d':' -f2 | sed 's/^[[:blank:]]*//;s/[[:blank:]]*$//')
BATTERY_ICON=$(upower -i /org/freedesktop/UPower/devices/battery_BAT0 | grep icon-name | cut -d':' -f2 | sed 's/^[[:blank:]]*'"'"'//;s/'"'"'[[:blank:]]*$//')

# Check battery level
if [ $POWER_NUM -le 40 ] && [ "$BATTERY_STATE" == "discharging" ]; then
	notify_user \
		--icon="$BATTERY_ICON" \
       		"Low Battery" \
		"Too few battery: $POWER. Start charging it up."
elif [ $POWER_NUM -gt 80 ] && [ "$BATTERY_STATE" == "charging" ]; then
	notify_user \
		--icon="$BATTERY_ICON" \
        	"Battery Level High" \
		"High battery level: $POWER. Stop charging."
fi

battery-level-check.timer

#
# Save this file as: /etc/systemd/system/battery-level-check.timer
#

[Unit]
Description=Battery check. If higher than 80% or lower than 40%, notify desktop user
Requires=battery-level-check.service

[Timer]
Unit=battery-level-check.service
# Runs every 5 minutes
OnCalendar=*:0/15

[Install]
WantedBy=timers.target