Hi, I am developing a regular expression that will test whether a string ends with test1234 or man2345.

E.g.  coolguy/most/test1234 is invalid where as coolguy/most/testtest is valid. The pattern I have developed is coolguy/most/.*(?<!(test[0-9]{4}|man[0-9]{4})). But I am getting error "Look-behind group does not have an obvious maximum length near index 54...".

I would appreciate your help on this.

- BR 

how do u plan to validate your strings:

1. one-by-one as a separate strings/lines

2. as parts of a text

?

You don't mention the language or regex engine that you are using, but going by the error message, some regex engines only allow fixed length look-behinds. Now each of the alternate paths you have are fixed length, but together they could be 7 or 8 characters long. this is a possible cause for your error.

If you have a regex engine that can handle lookbehind, you will also be able to use lookahead. Most regex's that allow lookahead also allow variable length lookahead patterns, so perhaps something like (untested):

coolguy/most/(?!.*?(test|man)\d{4}).*

may work.

Susan 

I just wanted to validate one by one string. I use java for regex.

I tried with your suggested pattern but it seems do not work.

In what way didn't it work? Can you post the code you are using together with your test data and the expected results?

Susan 

It works, earlier it was my mistake to apply it properly.

I use it in the following way

public boolean testPattern(String url){
        String regex = "coolguy/most/(?!.*?(test|man)\\d{4}).*";
        return Pattern.matches(regex, url));
    }