notepad++ how to keep all the line start with # and delete the rest of the line

Question

I kinda know how to keep delete all line start with # with the code

^[#].*

But I wonder how to do the reverse? keep all the line start with # and delete the rest.

Answer 1

In order to do that, you just use negated character class in your regex:

^[^#].+

[^#] means match everything except #, so please see picture below for better understanding:

Then just replace all, this will empty lines. So then you need to match new line characters only with ^\r\n (depending on operation system, it could be also ^\n) and again replace it with empty string: