> Sadly, this can't be done in-place, so you'll either need to use mv to
> replace /etc/conf.file with /etc/conf.file.new or repeat the loop (with
> no substitution) to copy /etc/conf.file.new into /etc/conf.file.
It can be done "inplace" with `rm' in place or `mv':
(rm /etc/conf.file;
while read line; do
echo ${line/old_word/new_word}
done >/etc/conf.file) </etc/conf.file
-- Stefan