UNIX for Dummies Questions & Answers

So, I need to do some summing. I have an Apache log file with the following as a typical line:

Code:

127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET       /apache_pb.gif HTTP/1.0" 200 2326

Now, what I'd like to do is a per-minute sum. So, I can have awk tell me the individual minutes, preserving the dates(since this is a multi-day log):

Code:

awk '{print substr($4,2,17)}' logfile

I can have it sum based on a single date:

Code:

awk 'substr($4,2,17) == "10/Oct/2000:13:55" && $9 ~ /^[0-9]$*/ && $10 ~ /^[0-9]$*/ {sum += $10}' logfile

...but what I'd really like to do is generate a new sum of $10 for each different instance of substr($4,2,17). This can be done by looping-- a foreach/for, etc-- and feeding minutes into the awk one at a time. The problem is that this method reads the file completely every pass through the loop. Ideally, I'd like to do it with a single pass. Any suggestions?