Regex lookahead for 'not followed by' in grep

Question

I am attempting to grep for all instances of Ui\\. not followed by Line or even just the letter L

What is the proper way to wr

Answer 1

The answer to part of your problem is here, and ack would behave the same way: Ack & negative lookahead giving errors

You are using double-quotes for grep, which permits bash to "interpret ! as history expand command."

You need to wrap your pattern in SINGLE-QUOTES: grep 'Ui\.(?!L)' *

However, see @JonathanLeffler's answer to address the issues with negative lookaheads in standard grep!