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Re: Capture only first match in regular expression

 
 
Peter Tuente
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      04-17-2009
Hi Zapanaz,

the default behaviour of regular expression terms is to be "greedy", so to
suppress this behaviour to become "not greedy" you have to apply a single
question mark "?" right after the desired expression(s). Sounds some kind of
complex, but I hope you get me

In your case the following should be sufficient:

# old: if($content =~ /.*(<a.*<\/a>).*/i){
$anchorContent = $1;

# new:
if($content =~ /.*?(<a.*?<\/a>).*/i){
$anchorContent = $1;

The effect is, that the first expression ".*" becomes not so greedy eating
all the possible chars (incl. one/some "<a" chars that prefix the last
occurrence of "<a" in the current line). Same with the second ".*".

Hope this helps

Bye.

PiT

"Zapanaz" <http://joecosby.com/code/mail.pl> schrieb im Newsbeitrag
news:(E-Mail Removed)...
> Excuse the cross-post, my server doesn't carry comp.lang.perl.misc but
> it looks like there is more activity there.
>
>
> The answer to this is probably staring me in the face ...
>
> I am parsing/page scraping some HTML. I know the first anchor tag <a>
> contains information I want.
>
> So I do this:
>
> if($content =~ /.*(<a.*<\/a>).*/i){
> $anchorContent = $1;
>
> This basically works the way I want, it matches an anchor tag and
> captures the content of it.
>
> But there are multiple anchor tags in the HTML. What I want is the
> first one, but what I get is the last one.
>
> I think I should be using one of these
>
> * Match 0 or more times
> + Match 1 or more times
> ? Match 1 or 0 times
> {n} Match exactly n times
> {n,} Match at least n times
> {n,m} Match at least n but not more than m times
>
> To be honest, I really don't know how (n) is actually supposed to
> look. Would I actually use /a(1)/ to match "a" only one time?
>
>
>
> --
> Zapanaz
> International Satanic Conspiracy
> Customer Support Specialist
> http://joecosby.com/
> Despite the strange appearance of the scooters, the Chinese ant-terror
> police are lethal in action.
>
> :: Currently listening to No 21 in C major K467 Allegro maestoso, 1785, by
> Mozart, from "Piano Concertos - Vladimir Ashkenazy"



 
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