Script to change blackhole to fail for all accounts

#! /bin/bash

grep -rl ‘:blackhole:’ /etc/valiases/ >> blackhole_files

for i in `cat blackhole_files`
do
grep -v ‘:blackhole:’ $i > tmpfile
echo ‘*: :fail: No such user here’ >> tmpfile
cat /dev/null > $i
cat tmpfile >> $i
done