Use regex backreference inside character except class [^]

Question

Lets take:

stringi = 'xnxx xnnx xnnxn'

My regex is: (n)[^n]

I want to make my regex a little more dynamic like that:

(n)[^\1] -\1 beeing the capt. grp 1

My desired result would be that:

How can I not match a NOT-\1 character?

Maybe `(n)(?!\1)`? You cannot use a backreference inside a character class. — Wiktor Stribiżew, Mar 19 '18 at 12:44
`\1` inside a character class denotes an octal sequence. You need to use lookaheads to achieve expected result. — revo, Mar 19 '18 at 12:46
See https://stackoverflow.com/questions/8055727/negating-a-backreference-in-regular-expressions — Wiktor Stribiżew, Mar 19 '18 at 12:47

score 1 · Accepted Answer · answered Mar 19 '18 at 12:45

1

using a negative lookahead, the . is to match any character as n length is one

(n)(?!\1).

answered Mar 19 '18 at 12:45

Nahuel Fouilleul

absolutely getting your idea. Very smart. Yet i don't get the same result as `(n)[^n]` on regex101.com. – Andre Elrico Mar 19 '18 at 12:48
I think I know why. The `.` does not consume new lines. Your solution is absolutely correct. Yet I know how I could tweak it. `(n)(?!\1)(?:.|[[:space:]])` – Andre Elrico Mar 19 '18 at 12:52
1

exactly `.` doesn't match newline by default but can be changed using flag `/s`, or depending engine `(?s).` – Nahuel Fouilleul Mar 19 '18 at 12:52

1 Answers1