How would I write a RegEx to:
Find a match where the first instance of a > character is before the first instance of a < character.
(I am looking for bad HTML where the closing > initially in a line has no opening <.)
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This does assume that your HTML is formatted in a way that allows all HTML to be on one line. So if someone starts an HTML tag and closes it on the next line you'd get a false positive although the HTML would be valid.spig– spig2010-08-17 14:53:19 +00:00Commented Aug 17, 2010 at 14:53
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3 Answers
It's a pretty bad idea to try to parse html with regex, or even try to detect broken html with a regex.
What happens when there is a linebreak so that the > character is the first character on the line for example (valid html).
You might get some mileage from reading the answers to this question also: RegEx match open tags except XHTML self-contained tags
Comments
Would this work?
string =~ /^[^<]*>/
This should start at the beginning of the line, look for all characters that aren't an open '<' and then match if it finds a close '>' tag.
3 Comments
Alexander Kjäll
what happens if the > was a closing one from the line above?
spig
I think that's a problem with the question. This will do what he asked it to do. To get the previous lines opens up the can-of-worms with using a regular expression to check a non-regular language.
spig
In perl/ruby and other languages you can use the "m" modifier which will treat the entire string as one line regardless of line breaks. I re-read his question and he doesn't necessarily specify that it would be all on one line.
string =~ /^[^<]*>/m^[^<>]*>
if you need the corresponding < as well,
^[^<>]*>[^<]*<
If there is a possibility of tags before the first >,
^[^<>]*(?:<[^<>]+>[^<>]*)*>
Note that it can give false positives, e.g.
<!-- > -->
is a valid HTML, but the RegEx will complain.
1 Comment
Mark Wilkins
It seems as if this won't catch this a line with: <tag1> badtag2>