bash script to monitor the size of a home directory

#!/bin/bash
#this is useful for seeing how far some directory has been used in real time 
#needs to have dialog utility installed and ncurses
while true;do
    cmd=`du -sh /home3/johndoe`
    echo $cmd
    x=` echo $cmd |cut -d ' ' -f 1`
    #if [ $x == "10G" ]; then
    #   dialog --messagebox "10 gigs" 100 200;
    #   exit;
    #fi
    val=${x%"G"}

    #echo $val
    echo "$val*100/20" | bc | dialog --gauge 6 70 0
    sleep 1;
done