home.public.bin/bin/whoIsOnMySubnet

#! /bin/bash
#
# A quick script to see who (DNS names) are on the same subnet.  
# Assumes eth0 and /24.
#
# Usage: onMySubnet [ip]
#
# George Jones <gmj@pobox.com>, Wed Sep 30 05:50:02 2015
#

eth0Addr=`ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}'`

addrWith4Octets="${1:-${eth0Addr}}"


addrWith3Octets=`echo $addrWith4Octets | cut -d"." -f1-3`

i=1;
while [ "$i" -lt 255 ]; do 
    host ${addrWith3Octets}.$i | grep -v NX; 
    i=$((i+1)); 
done