#!/bin/bash 

EXT0="jpg"
COUNTER=1
EXT1="jpg"

for name0 in `ls *.$EXT0` 
do 

#name1=`echo $COUNTER.$EXT0`
printf -v name1 "%03d.%s\n" $COUNTER $EXT1
echo $name0 $name1
mv $name0 $name1
let COUNTER=COUNTER+1
 
done