low battery warning, goes into ~/.config/sxmo/hooks/sxmo_hook_battery.sh

sxmo_hook_battery.sh

  GNU nano 7.2                               .config/sxmo/hooks/sxmo_hook_battery.sh                                          
#!/bin/sh
# configversion: d7a31b6b01150a2b1ad3e57f556a5de6

load_data() {
        data="$(upower -i "$1" | grep . | sed -e 's|^ \+||' -e 's|: \+|:|')"
        type="$(printf "%b" "$data" | grep -m1 -v : | sed -e 's|^ \+||')"
}

data_get() {
        printf "%b" "$data" | grep "^$1:" | cut -d: -f2
}

device_changed() {
        name="$(data_get "native-path")"
        state="$(data_get "state")"
        percentage="$(data_get "percentage" | cut -d% -f1)"

        if [ -z "$name" ] || [ -z "$state" ]; then
                return
        fi

        if [ "$state" = unknown ]; then
                return
        fi

        sxmo_hook_statusbar.sh battery "$name" "$state" "$percentage"
}
# battery low warning
PERCENTAGE=$(upower -d | awk '/percentage/; /^$/ {exit}' | sed 's/[^0-9]//g')
STATE=$(upower -d | awk '/state/; /^$/ {exit}' |  sed 's/state://g;s/ //g')

if [ $STATE = "discharging" ] && [ $PERCENTAGE -lt 8 ]; then
  notify-send -t 5000 --urgency=critical "BATTERY is LOW" "(+_+) I will die soon"
fi

object="$1"
event="$2"

if [ "$type" != "battery" ]; then
        exit
fi

case "$event" in
        "device changed")
                device_changed "$object"
                ;;
esac