How to replace within a capture group

Question

I am modifying an existing HTML doc. I'm doing things like adding a table of contents etc.

I have a heading with this ID: id="transcending intellectual limitations" (for real!)

I want to be able to find the whole ID, and then replace the spaces with hyphens.

It would be simple if I had just the IDs but I don't want to remove all the spaces in the whole document.

I'm reasonably new to regex, I'm using Sublime's find and replace to do this.

Answer 1

You can use

(?:\bid="|(?!^)\G)[^\s"]*\K\s+ 

And replace with anything you need to replace spaces with.

The (?:\bid="|(?!^)\G) pattern sets the initial boundary: either id=" or the end of the last successful match. This pattern presents an alternation list with two alternatives. \b matches a word boundary so that id=" is matched as a whole word. The \G operator matches at the start of the string and after ech successful match. To exclude the start position, a negative (?!^) lookahead is added (not followed with a string start position). See more about \G in "Where You Left Off: The \G Assertion".

The [^\s"]* matches zero or more characters other than whitespace and a quote.

The \K operator makes the regex engine omit all the text matched so far from the match buffer.

The \s+ finally matches one or more whitespaces that will be replaced.

Regex101 Demo