regex to find pattern not inside another pattern

Question

I'm trying to write a regex to find all ID selectors in a CSS file. Basically, that means any word that starts with a #, so okay

#\w+

Except ... color specifiers can also start with a #. So what I really want is all words that start with a # that are NOT between { and }. I can't figure out how to say this.

I'm doing this in Notepad++ so I need that flavor of regex.

BTW my real objective is to delete everything that's not an ID selector from the file, so I end up with just a list of selectors. My first try was

Find: [^#]*(#\w+)
Replace: \1\r\n

... and then hit Replace All.

But then I ran into the color problem.

Update

Someone asks for an example. Ok:

Input:

.foo {max-width: 500px;}
#bar {text-align: left;}
.splunge, #plugh {color: #ff0088;}

Desired output:

#bar
#plugh

Note the point is that it includes the two "pound strings" that come outside of braces but not the one that comes inside braces.

Considering FFFFFF is a valid HTML ID, I don't see how you could possibly differentiate the two. What kind of ID's are you targeting? Are you specifically looking for ID's that are the target of a call to a method? (e.g. $("#myID"), document.querySelector("#myID"), etc.) knowing your goal or desired outcome may help us suggest alternative ideas. — Joseph Marikle
– Joseph Marikle, Commented Aug 9, 2018 at 21:05
@JosephMarikle Yes, I quickly realized I couldn't base the test on "looks like a valid color code". #FFFFFF may be an unlikely ID, but certainly not impossible. And, say, #BAD or #FACE02 could certainly turn up. That's why I was thinking that if it's between braces, than I could say it's not an ID and so not interesting. I guess that could skip media queries, now that I think about it. — Jay
– Jay, Commented Aug 9, 2018 at 21:17
@JosephMarikle My ultimate goal is that I have to find all CSS that references an ID, and that ID is in a Visual Basic user control. Possible to go at it from the other direction: find all the IDs in VB UCs and then search the CSS for them. I'm not sure that that would be any easier. — Jay
– Jay, Commented Aug 9, 2018 at 21:19

Joseph Marikle · Accepted Answer · 2018-08-09 21:42:25Z

3

What about this? You could use a lookahead expression:

#\w+(?=[^}]*?{)

It ensures that a { follows the match (indicating that the match is part of a selector), but not after a } character (excluding any matches against color declarations in the CSS).

#: match must begin with a #
\w+: match one or more word characters (might need tweaked. \w is equivalent to [A-Za-z0-9_])
(?=...): positive lookahead
[^}]*?: Any character not matching }
{: the { character

https://regex101.com/r/Di43hX/3

edited Aug 9, 2018 at 21:42

answered Aug 9, 2018 at 21:30

Joseph Marikle

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