Monitoring battery discharge state in Ubuntu

Details of battery state we can examine by following command: upower -i $(upower -e | grep BAT)

The battery discharge state (remaining load percentage) we can check as below: upower -i $(upower -e | grep BAT) | grep -E "percentage" | awk '{ print $2 }'

Script alerting about hardly battery discharging:

#!/bin/sh

BATTERY_FILE=$(upower -e | grep BAT)

while true; do
    STATE=$(upower -i "$BATTERY_FILE" | grep -E "state" | awk '{ print $2 }')
    PERCENTAGE=$(upower -i "$BATTERY_FILE" | grep -E "percentage" | awk '{ print $2 }' | sed 's/%//g')

    if [ "x$STATE" = "xdischarging" ]; then
        echo "Battery discharging: ${PERCENTAGE}% left"
        if [ $PERCENTAGE -lt 8 ]; then
            mpg123 ~/Download/beep-02.mp3
        fi
    fi
    sleep 5
done;