dont grep, just run iptables -L or if you wish to monitor and dig through the output redirect it to a file then vi the file...
Code:
iptables -L >> IPTABLES
vi IPTABLES
then you can line throug or use the search function built into vi. to search with vi just hit the / key then without a space type your search...
to advance to the next line with that search string just hit the 'n' key.