Simple (bash) script to check the number of iptables rules for Linux

check-iptables.sh

#!/bin/bash                                                                                                                         
#                                                                                                                                   
# Simple (bash) script to check the number of iptables rules for Linux                                                              
#                                                                                                                                   
# You could run this at system start (possibly after a few second delay) or                                                         
# as a cron job every minute or so. On any given system, it's probably not                                                          
# a normal situation that there exist no (zero) iptables rules.                                                                     
#                                                                                                                                   
# Released to the Public Domain, Joaquim Homrighausen, 2021-09-16                                                                   
# (If you break it, you own all the pieces.)                                                                                        
#                                                                                                                                   
                                                                                                                                    
rules=$(iptables -n --list --line-numbers | sed '/^num\|^$\|^Chain/d' | wc -l)                                                      
                                                                                                                                    
if [[ $rules == "0" ]]; then                                                                                                        
    echo "No rules found"                                                                                                           
    #insert your command to restore iptables rules here                                                                             
    #e.g. iptables-restore < /etc/iptables.up.rules                                                                                 
    exit 1                                                                                                                          
else                                                                                                                                
    #this could of course be commented out if you don't                                                                             
    #want a verbal message when all is good                                                                                         
    echo "$rules rule(s) found"                                                                                                     
    exit 0                                                                                                                          
fi