docker-mailserver/target/bin/addmailuser

#! /bin/bash

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

USER="$1"
shift
PASSWD="$@"

usage() {
	echo "Usage: addmailuser <user@domain> [<password>]"
}

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

escape() {
	echo "${1//./\\.}"
}

[ -z "$USER" ] && { usage; errex "no username specified"; }
expr index "$USER" "@" >/dev/null || { usage; errex "username must include the domain"; }

# Protect config file with lock to avoid race conditions
touch $DATABASE
( 
  flock -e 200

  grep -qi "^$(escape "$USER")|" $DATABASE 2>/dev/null &&
    errex "User \"$USER\" already exists"

  if [ -z "$PASSWD" ]; then
    read -s -p "Enter Password: " PASSWD
    echo
    [ -z "$PASSWD" ] && errex "Password must not be empty"
  fi

  HASH="$(doveadm pw -s SHA512-CRYPT -u "$USER" -p "$PASSWD")"
  echo "$USER|$HASH" >> $DATABASE
) 200<$DATABASE