Thanks to Arjun, now I know the existence of ns_logroll :D...
and it works..I haven't try the script yet..but thanx a lot.
My thanx also goes to Bob,Andrew,Patrick.
I actually dont like to look those errors thru Vi,emacs nor less...
instead, I used a script which I can observe those errors thru browser
(which is much easier to me rather than invoking those tools).
The problem was, whenever the file is TOOOO BIGGO, the scripts failed :( .
Thats why I need to know how to roll the log ...
thanx anyway