(OK) shell script—Find a Rogue DHCP Server—tcpdump/dhclient—nmap

# . find_rogue_dhcp.sh &

#! /bin/sh
    # tcpdump -i enp13s0 -nev udp port 68 >> /tmp/rogue 2>&1 &
    # touch /tmp/rogue_dhcp_ip
    # . find_rogue_dhcp.sh &

    while true
    do
    echo > /tmp/rogue
    dhclient -r
    dhclient >/dev/null 2>&1
    sleep 2
    grep '192.168' /tmp/rogue >> /tmp/rogue_dhcp_ip
    done