Ugly kludge for parsing a given log file and returning the most common IP-like strings.

Filter_log_for_IPs

grep -o -E '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' ACCESS_LOG.TXT | grep -v "127.0.0.1" | sort | uniq -c | sort -n -r | head -n 5

# Bonus kludge for parsing multiple gzipped logs for the same. Also prints the logfile datestamp for each file as well:
for i in {1..20}; do date -r ACCESS_LOG.$i.gz; zgrep -o -E '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' \ACCESS_LOG.log.$i.gz | grep -v "127.0.0.1" | sort | uniq -c | sort -n -r | head -n 5; done