{tech}.Ben Buckman.net

Say you wanted to count the number of unique IP addresses hitting your Apache server. It's very easy to do in a Linux (or compatible) shell.

First locate the log file for your site. The generic log is generally at /var/log/httpd/access_log or /var/log/apache2/access_log (depending on your distro). For virtualhost-specific logs, check the conf files or (if you have one active site and others in the background) run ls -alt /var/log/httpd to see which file is most recently updated.

Then spit out one line to see the format:
tail -n1 /var/log/httpd/access_log

Find the IP address in that line and count which part it is. In this example it's the 1st part (hence $1):

cat /var/log/httpd/access_log | awk '{print $1}' | sort | uniq > /var/log/httpd/unique-ips.log

You'll now have a list of sorted, unique IP addresses. To figure out the time range, run
head -n1 /var/log/httpd/access_log
to see the start point (and the tail) syntax above for the end point.)

To count the number of IPs:
cat  /var/log/httpd/unique-ips.log | wc -l

To paginate:
more  /var/log/httpd/unique-ips.log

Have fun.