docker-mailserver/target/bin/listmailuser

#! /bin/bash

DATABASE=${DATABASE:-/tmp/docker-mailserver/postfix-accounts.cf}

errex() {
	echo "$@" 1>&2
	exit 1
}

[ -f $DATABASE ] || errex "No postfix-accounts.cf file"
[ -s $DATABASE ] || errex "Empty postfix-accounts.cf - no users have been added"

# Lock database even though we are only reading
(
  flock -e 200
  awk -F '|' '{ print $1; }' $DATABASE
) 200<$DATABASE