How to make the pattern do not capture when the closing tag is invalid

Question

I have the following expression to validate a specific tag:

<TAG(:([^:>\\s]*))?>

This pattern should be valid for: <TAG:abc>, <TAG:dfg>, etc

How to make this expression be invalid in this case: <TAG:hij>k> (k> = invalid closing tag).

Which language are you running. If it's java then you need to escape the backslash one more time. — Avinash Raj
– Avinash Raj, Commented Oct 7, 2014 at 6:21
\\s inside a character class would mean a literal \ and an literal s character. It wouldn't match a space character. — Avinash Raj
– Avinash Raj, Commented Oct 7, 2014 at 6:25

Avinash Raj · Accepted Answer · 2014-10-07 06:26:40Z

1

Just use a lookahead after to your regex to ensure that the tag must be followed by a space or end of the line anchor.

<TAG(:([^:>\\s]*))?>(?=\s|$)

OR

<TAG(:([^:>\s]*))?>(?=\s|$)

answered Oct 7, 2014 at 6:20

175k32 gold badges247 silver badges289 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

worked perfectly! RegEx is something that I need to study a little more... Thank you to solve a little bug in my library =D