Regex not start with dot or end with dot

From your previous question, you should be able to use:

^[^.].*[^-_.]$

But if you want to be able to match a 1 character string, you will need negative lookaheads:

^(?![.])(?!.*[-_.]$).+

And if you want to match empty strings too, simply use * instead of +.

^(?![.])(?!.*[-_.]$).*

Using negative lookaheads to assert your requirements for the string:

^(?!^\.)(?!.*[-_.]$)[a-zA-Z0-9]+$

Related