battery-age.sh

#!/bin/env bash

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# Copyright (C) 2019 BanditHijo
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
# more details.
#
# You should have received a copy of the GNU General Public License along with
# this program. If not, see http://www.gnu.org/licenses/.

# author  : Rizqi Nur Assyaufi
# website : https://bandithijo.com
# email   : bandithijo@gmail.com
# created : 2018

#read -p "Enter your birth year.  Example: 1900 : " year
#read -p "Enter your birht month. Example: 06 " month
year=2019
month=05

yearnow=$(date '+%Y')
monthnow=$(date '+%m')

agey=$(($yearnow-$year))
agem=$((10#$monthnow-$month))

if [[ $((10#$agem)) -lt 0 ]] ; then
   agem=$(($monthnow-$month+12))
else
   agem=$((10#$monthnow-$month))
fi

echo "$agey""Y" "$agem""M"