#!/bin/sh

ls *.pbm  | sort | nl -w 4 -s ";" | sed "s/^\([^;]*\);\(.*\)$/mv \2 \1.pbm /gi" | bash

if [ -e 100.pbm ]
then
for i in [1-9][0-9][0-9].pbm; do mv $i 0$i; done
fi

if [ -e 10.pbm ]
then
for i in [1-9][0-9].pbm; do mv $i 00$i; done
fi

for i in [1-9].pbm; do mv $i 000$i; done