regex negative look-behind

UPD: I need to check if @if(Medellin) so take "City Medellin" but if @if(null) don’t take anything

Here is my pattern:

(?<!@if\(null\)).*?@end$

Testing strings:

@if(Medellin) City Medellin @end

@if(null) City Medellin @end

I understood that first checks right side, and it takes all string 🙁

>Solution :

You can use

@if\((?!null\))\w+\)\s*(.*?)\s*@end\b

See the regex demo. To match across lines, you will need either (?s)@if\((?!null\))\w+\)\s*(.*?)\s*@end\b or @if\((?!null\))\w+\)\s*([\w\W]*?)\s*@end\b.

Details:

• @if\( – a @if( string
• (?!null\)) – a negative lookahead that fails the match if there is null) string immediately to the right of the current location
• \w+ – one or more word chars
• \) – a ) char
• \s* – zero or more whitespaces
• (.*?) – zero or more chars as few as possible
• \s* – zero or more whitespaces
• @end\b – @end whole word.