regex with optional data at the front

Question

I have a regex that looks like this

((1010xxx)?(\d{11}|\d{10}|\d{7})+)

Basically I want it to match

8085551234
5551234
10102338085551234

and it should fail on
1010233

This is more for validation being done on an xsd than an actual matcher.

PS. I am trying to match US telephone numbers 7 - 11 digits long with an optional 1010xxx at the front. Also if it is 1010xxx it should not pass. xxx is any 3 digits.

Answer 1

If all you want is to make sure that it's a 7, 10, or 11 digit string, making sure that if it's only 7 digits it doesn't start with '1010', you can use a negative lookahead assertion before your match on \d{7}, i.e.:

((\d{11}|\d{10}|(?!1010)\d{7})+)