Capture with negative look behind

Question

Let's assume I have the following subject:

abcdef ghidef

and I want to match word ending with def not preceeded by abc (in this case it would be ghidef). How can I match this?

When I use:

(?<!abc)def

I'm getting the 2nd def but I'm not getting ghi here.

Answer 1

No need of lookbehind. You can use with a negative lookahead:

\b(?!abc)\w*def\b

RegEx Demo

RegEx Breakup:

• \b - assert a word boundary
• (?!abc) - is negative lookahead that asserts a word doesn't start with abc after \b (word boundary)
• \w* - match 0 or more word characters
• def - ending text of word is def
• \b - word boundary