Bash script for renaming files en masse

#! /bin/bash
x=0
for i in `ls $1/*.$2`
do
mv $i `printf "%03x.$2" $x`
x=$(($x+1))
done

Usage : (say call the script a.sh )
./a.sh /var/www/html/images jpeg
will sequentially rename all jpeg files in /var/www/html/images to 001.jpeg 002.jpeg etc.