#!/bin/bash
# Current Size
CURRENT=$(cat ~/currentSize.txt)

# check for new size of the folder
GET=$(du -sB GB [insert path here] | grep -Eo '[0-9\]+' > newSize.txt)
NEW=$(cat newSize.txt)
WRITE=$(cat ~/newSize.txt > ~/currentSize.txt)

if [ $NEW -gt $CURRENT -a $NEW -ne $CURRENT ]; then
        $WRITE
        [run thing here]
fi