Re: Regex advice

Steve Bertrand wrote:
> Hi everybody,

Hello,

> I am far from a regex guru, so I know that I can get advice on how to 
> learn to improve my regex knowledge so I can better my currently working 
> code to protect against failure in the future. I would appreciate some 
> criticism, with explanations as to the changes if possible.
> 
> I've made it as brief as possible, with hopefully enough context (sorry 
> if it wraps):
> 
> 
> while (<LOG>) {
> 
> if (/.*simscan~\[\d+\]~([\w|\s]+).*?~(\d+\.\d+)s~.*?~(.*?)~(.*?)~(.*)/) {

The .* pattern at the beginning is useless as it causes unnecessary 
back-tracking, just remove it.  The character class [\w|\s] includes 
both the '|' and '_' characters but it doesn't appear that that field 
would normally contain either a '|' or a '_' character.


>                 $result   = $1 if $1;

([\w|\s]+) will always match at least one character so the only way that 
$1 can be false is if it contains '0'.


>                 $scantime = $2 if $2;

(\d+\.\d+) will always match at least three characters so it can never 
be false so the test is superfluous.


>                 $ip       = $3 if $3;
>                 $from     = $4 if $4;
>                 $to       = $5 if $5;

If $3, $4 or $5 are false they will contain either '' or '0'.



John
-- 
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order.                            -- Larry Wall