Copy of script from here http://blog.aclarke.eu/2011/09/21/a-simple-treesize-shell-script-for-linux/
I needed a simple way of finding out why my disk was full and a simple way of getting this script onto my unix host.
All credit to the original author.
Navigate to the level that you want to query - for me this was /
Then run the script:
sudo sh /home/pi/LinuxTreeSize/treesize.sh