Regex matching a non-empty string that is not equal to certain value

Question

I'm trying to write a regex to match any string that is not empty or equals to www.

Example:

www => don't match
ww => match
adwww => match
wwwad => match
abcde => match

My regex:

(.+)(www)

How can I fix my regex?

Answer 1

You need a lookahead based regex:

^(?!www$).+

See the regex demo.

Details:

• ^ - start of string
• (?!www$) - the string cannot be equal to www
• .+ - 1 or more characters (other than a line break if you do not use a DOTALL modifier)