Trying to create a regex where a field should contain minimum 4 characters(only alphabets [a-zA-Z]) where

1. first 4 alphabets should not repeat. eg aaaa,zzzz not acceptable
2. first 4 characters should not contain space, numbers, special characters
3. afterwhich anything is fine

I tried following expression but 1 case is failing which is (a123,a@#!): ^(?=.{1,4}$)(([a-zA-Z]){1,4}\2?(?!\2)) [a-zA-Z0-9!@#$&()\-`. ,"]

CodePudding user response：

You might write the pattern as:

^(?!(.)\1{3})[a-zA-Z]{4}.*

Explanantion

• ^ Start of string
• (?!(.)\1{3}) Negative lookahead, assert not 4 of the same characters
• [a-zA-Z]{4} Match 4 chars a-z A-Z
• .* Match the rest of the line

Regex demo