How to use Perl Regex to detect <p> inside another <p>
I am trying to parse a "wrong html" to fix it using perl regex.
The wrong html is the following: <p>foo<p>bar</p>foo</p>
I would like perl regex to return me the : <p>foo<p>
I tried something like: '|(<p\b[^>]*>(?!</p>)*?<p[^>]*>)|'
with no success becaus开发者_如何学Goe I cannot repeat (?!</p>)*?
Is there a way in Perl Regex to say all charactère except the following sequence (in my case </p>)
Try something like:
<p>(?:(?!</?p>).)*</p>(?!(?:(?!</?p>).)*(<p>|$))
A quick break down:
<p>(?:(?!</?p>).)*</p>
matches <p> ... </p> that does not contain either <p> and </p>. And the part:
(?!(?:(?!</?p>).)*(<p>|$))
is "true" when looking ahead ((?! ... )) there is no <p> or the end of the input ((<p>|$)), without any <p> and </p> in between ((?:(?!</?p>).)*).
A demo:
my $txt="<p>aaa aa a</p> <p>foo <p>bar</p> foo</p> <p> bb <p>x</p> bb</p>";
while($txt =~ m/(<p>(?:(?!<\/?p>).)*<\/p>)(?!(?:(?!<\/?p>).)*(<p>|$))/g) {
print "Found: $1\n";
}
prints:
Found: <p>bar</p>
Found: <p>x</p>
Note that this regex trickery only works for <p>baz</p> in the string:
<p>foo <p>bar</p> <p>baz</p> foo</p>
<p>bar</p> is not matched! After replacing <p>baz</p>, you could do a 2nd run on the input, in which case <p>bar</p> will be matched.
I concur with Andy. Parsing nontrivial HTML with regexps is a world of pain.
Have a good look at HTML::TreeBuilder::XPath and HTML::DOM for making structural changes to HTML documents.
This regexp:
<p>(?:(?!</p>).)*?<p>
when matched with
<p>foo<p>bar</p>foo</p>
results in
<p>foo<p>
If you're trying to validate HTML then consider a module like HTML::Tidy or HTML::Lint.
Perhaps Marpa::HTML would help you. Read some interesting abilities it has on the author's blog about it. The short of it is that the parser works with the interpreter (I probably am getting some of the semantics incorrect) to figure out what should be present based on what CAN be present at a certain logical place in the code.
The examples shown therein fix similar problems as you seem to be dealing with in a much more consistent way than employing regexes which will inevitably suffer from edge cases.
Marpa::HTML comes with a command-line utility, built using the module, called html_fmt. This implements a parsing engine to fix and pretty-print html. Here is an example. If 'bad.html' contains <p>foo<p>bar</p>foo</p> then html_fmt bad.html gives:
<!-- Following start tag is replacement for a missing one -->
<html>
<!-- Following start tag is replacement for a missing one -->
<head>
</head>
<!-- Preceding end tag is replacement for a missing one -->
<!-- Following start tag is replacement for a missing one -->
<body>
<p>
foo
</p>
<!-- Preceding end tag is replacement for a missing one -->
<p>
bar
</p>
foo
<!-- Next line is cruft -->
</p>
</body>
<!-- Preceding end tag is replacement for a missing one -->
</html>
<!-- Preceding end tag is replacement for a missing one -->
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