Last Activity IPFW

[akamos]

Hi everbody!
I search for a possibility to get the Last Activity of a user through the command line. I still understood how ipfw works and got there some information.
I want to create a little sh script which shows all users and their last activity.

For example
ipfw -x 2 table 1 list
ipfw -x 2 table 1 entrystats 192.168.56.45

But where can I get the timestamp like in the PHP-function "captiveportal_get_last_activity" in captiveportal.inc? I tried to find out how this function is made, but got no solution.

Thanks for every help!
Akamos