How do I know what variables are available to me with external commands?  All of the examples use $SRC, but a few of the config files claim there are many more.  How would I find what these are?

Specifically, I'd like to use the source IP address where the packet originated (not the one specified in the message) and I'd like the username.  Is this possible? 

I'd like to be able to do something along the lines of:

EXTERNAL_CMD_OPEN: echo "$SRC $USERNAME" > /path/to/foo.txt;

I see the message containing everything I want go through in the syslog,
fwknopd: received valid Rijndael encrypted packet from: 127.0.0.1, remote user: testuser, client version: 1.9.11 (SOURCE line num: 27)

But, the $SRC variable does not reference the ip in the syslog message, it seems morpheus can't parse the external IP from the web anymore and I have no idea how to get at the username variable.

- Steve