Regular Expression question

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Expert

I swear I surf a lot of regular expression stuff to study but I find regular expression topic is too difficult to me understand. Any good suggestion for me?

Anyone can explain to me why this <p[^>]*> can simply remove the start <p> or <p attr="">? And what could I do, if I want make it from

<div style="float: left; width: 350px; border: 1px solid #000000;" class="star1">abcdk</div>

to this

<div class="star1">abcdk</div>

Thanks in advance.

Read some tutorials, experiment, and don't parse HTML with regex. ;-) I'd suggest http://perldoc.perl.org/perlretut.html even if you are not into Perl. — Qtax, Jul 14 '11 at 02:54
Using regex to parse HTML/XML is a losing battle. It's like using a screwdriver to hammer nails. You can do it with a lot of work but it's not a good solution. Please read the first answer to http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags — Jim Garrison, Jul 14 '11 at 06:03
[The `` cannot hold it is too late](http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454#1732454). — Maxpm, Jul 14 '11 at 11:41

Ryan Stewart · Accepted Answer · 2011-07-14T03:28:20.243

Suggestion: Play around with a regex tester to get the hang of what matches what.

Jason's explanation was good, but maybe not in-depth enough for you if you're just starting out with regexes. Let's take <p[^>]*> a piece at a time:

< has no special meaning to regex engines, so it means it just matches a single <
p is the same: match a single p
[ is a special character. Square braces in regex mean "any of these". For instance, the regex [abc] would match any single character that is 'a', 'b', or 'c'.
^ is a special character with two possible meanings. When inside of square brackets, like it is here, it's a simple negation. Whereas [abc] would match any single character mentioned, [^abc] would match any single character not mentioned.
> has no special meaning: just match a single >
] should be obvious to you by now: it closes the opening [
* is a special character that says match 0 or more of what came before it; that means it could match nothing, or it could match a huge amount of stuff, as long as it all matches what comes before the *.
> still no special meaning, like earlier

So we can break <p[^>]*> into three pieces, and we can say that it matches any series of characters:

<p: that starts with a literal <p,
[^>]*: which is followed by 0 or more characters that are not a >,
>: and which ends with a literal >.

Oh, and http://www.regular-expressions.info is one of the best regex guides I've ever found online.

Ah, I see. When I first looked at it, it must not have been showing the code blocks. There was nothing there. — Ryan Stewart, Jul 14 '11 at 02:42
Updated my answer to account for the question that I can now see. — Ryan Stewart, Jul 14 '11 at 03:13
Ryan, you are my great teacher. Make everything so clear to me. Really appreciate it. — user610983, Jul 14 '11 at 03:23
Glad I could help :) Please remember to accept an answer if your problems are cleared up. — Ryan Stewart, Jul 14 '11 at 03:30

score 0 · Answer 2 · answered Jul 14 '11 at 02:32

<p[^>]*>

Matches <p with any character except > ending with a >. In this case a <p> tag with or without attributes.

For a <div> tag, you could simply modify the regex above. A simple example being:

<div[^>]* class="star1">

For something more flexible (i.e. class attribute doesn't have to be at the end):

<div[^>]*class="star1"[^>]*>

I'd encourage you to learn more about regular expressions. They are a very powerful tool.

Regular Expression question

2 Answers2