//github.com/equaeghe/batenergy fork with some fixes and a notify-send

batenergy.sh

#!/usr/bin/env bash

FILE=/tmp/batenergy.dat
ADP=(/sys/class/power_supply/A*)
BAT=(/sys/class/power_supply/BAT*)
USER="edu"
USERID=$(id -u ${USER})

[[ -e $BAT ]] || exit

state=$1
sleep_type=$2

if [[ $state == "post" ]]; then
        sleep 2
fi

now=`date +'%s'`

# Read an energy in mWh from /sys/class/power_supply.
# Some firmware only reports charge (in µAh), in which case we convert using a stable voltage.
read_energy() {
        local when=$1
        local -n var=energy_$when
        if [[ -e $BAT/energy_$when ]]; then
                (( var = $(< "$BAT"/energy_$when) / 1000 )) # mWh
        else
                if [[ -z $voltage_ref ]]; then
                        if [[ -e $BAT/voltage_min_design ]]; then
                                voltage_ref=$(< "$BAT"/voltage_min_design)
                        else
                                voltage_ref=$(< "$BAT"/voltage_now)
                        fi
                fi
                (( var = $(< "$BAT"/charge_$when) * voltage_ref / 1000000000 )) # mWh
        fi
}

read_energy now
read_energy full

if [[ -f $ADP/online ]]; then
        read online < "$ADP"/online

        if (( online )); then
                echo "Currently on mains."
        else
                echo "Currently on battery."
        fi
fi

case $state in
"pre")
  echo "Saving time (${now}) and battery energy (${energy_now}) before sleeping ($sleep_type)."
        echo $now > $FILE
        echo $energy_now >> $FILE
        ;;
"post")
        exec 3<>$FILE
        read prev <&3
        read energy_prev <&3
        rm $FILE
        time_diff=$(($now - $prev)) # seconds
        if (( time_diff <= 0 )); then time_diff=1; fi
        days=$(($time_diff / (3600*24)))
        hours=$(($time_diff % (3600*24) / 3600))
        minutes=$(($time_diff % 3600 / 60))
        (( energy_diff = energy_now - energy_prev )) # mWh
        (( avg_rate = energy_diff * 3600 / time_diff )) # mW
        energy_diff_pct=$(bc <<< "scale=1;$energy_diff * 100 / $energy_full") # %
        avg_rate_pct=$(bc <<< "scale=2;$avg_rate * 100 / $energy_full") # %/h
        MESSAGE="Duration of $days days $hours hours $minutes minutes sleeping ($sleep_type).
Energy difference = ${energy_now} - ${energy_prev}
Battery energy change of $energy_diff_pct % ($energy_diff mWh) at an average rate of $avg_rate_pct %/h ($avg_rate mW)."
        echo "$MESSAGE"
        # Wait for the user session and notification daemon to be fully ready after thaw
        sleep 5
        sudo -u ${USER} DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/${USER}/bus notify-send "Battery resume stats" "${MESSAGE}"
        ;;
esac