External Tables - Help Please

I am using Oracle external tables to read alert log to display the content on a webpage

Oracle Version :oracle 9.2.0.4 and oracle10grel2

Looking for a sql to read Today's alert log contents only,

Looked at uinsg AWK to create just todays file only, unless I run this every 2 mins or so, I wont see the latest alertlog info, dont want to go this route unless
there is no other option

Here is the SQL right now I am using to read last 100 lines, even this the Timestamp comes after the messages becase of DESC, not in the right order

select rownum,text as "alert_${DB}.log" from (select alert_log.text, rank() over (order by rownum desc) r from alert_log) where r <= 100

Appreciate your help

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Regards & Thanks
BN

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