domain_name from dhcp_packet of first active network interface https://jamfnation.jamfsoftware.com/discussion.html?id=4112

domain_name.sh

#!/bin/bash
#set -x
declare -x ipconfig="/usr/sbin/ipconfig"
for (( N = 0 ; N <=3; N++ )) ; do
  declare DOMAIN_NAME="$($ipconfig getoption en$N domain_name 2>/dev/null)"
  [ "${#DOMAIN_NAME}" -gt 0 ] && break
done
printf "<result>%s</result>\n" "$DOMAIN_NAME"