#! /bin/sh
# begin with an empty file
cp /dev/null users.txt
# add real users
getent passwd | awk -F: '{print $1}' >> users.txt
# dump all your aliases
for db in /etc/mail/aliases*.db
do
  makemap -u hash $db | awk '{print $1}' >> users.txt
done
# dump the table of virtual users
db=/etc/mail/virtusertable.db
makemap -u hash $db | awk '{print $1}' | \
      awk -F@ '/@example.com/ {print $1}' >> users.txt