#!/bin/bash

refids=$(grep "<refentry id=" ref/*.xml | cut -f 2 -d ':' | cut -f 2 -d "\"")

for r in $refids
do
    s=$(echo $r | sed -e 'y/QWERTYUIOPASDFGHJKLZXCVBNM/qwertyuiopasdfghjklzxcvbnm/')
    echo "$r - $s"
    for f in ref/*.xml
    do
        sed -e "s/$r/$s/g" $f > $f.new
        mv $f.new $f
    done
done