show iptables rules clearly

fw.sh

#!/usr/bin/env bash

set -e
set -o pipefail

BOLD="$(printf "\x1B[1m")"
CLEAR="$(printf "\x1B[0m")"

ruledir="$(mktemp -d /tmp/fw.XXXXXX)"

trap "{ rm -f $ruledir/*; rmdir $ruledir; exit; }" EXIT

for ip in ip ip6; do
  for chain in $("$ip"tables -S | grep -- -[PN] | awk '{ print $2 }'); do
    "$ip"tables -S "$chain" | nl -v0 >> "$ruledir/$ip"
    echo >> "$ruledir/$ip"
  done 
done

diff -W "$(tput cols)" --side-by-side "$ruledir/ip" "$ruledir/ip6" \
  | sed 's/ 0	-[PN]/  	  /g; s/ACCEPT\|DROP\|RETURN\|REJECT/'$BOLD'&'$CLEAR'/g'