Thanks for your patience in this Charles, I really appreciate it.
Maybe it would help to explain what I'm trying to do here.
OWWNOGUI is an app that runs on my linux box. It gathers weather data from
a 1-wire Dallas sensor array (wind speed, direction and temp). Whenever it
is run, it normally outputs its data to the console and makes a log entry
that is identical to the console output.
What I'm doing is piping the console output to a file, parsing that file
for the weather data as "current conditions" and writing an html file for a
webpage. I want to take the data from the previous day (from the log
entries), average it and display it on the same webpage as "yesterday's
conditions". All this will be cron'd to run every 5 minutes.
My only real hangup has been how to identify the log entries starting with
yesterday's date (relative to the localtime of course). It struck me that
since each line in the log starts with mm/dd/yy, all I really need do is
check the dd field, since that will alway be unique relative to today's date.
Does this clarify things or have I just muddled things more?