grep with regex for phone number

Question

I would like to get the phone numbers from a file. I know the numbers have different forms, I can handle for a single one, but don\'t know how to get a uniform regex. For ex

Answer 1

+?(1[ -])?((\d{3})[ -]|(\d{3}[ -]?)){2}\d{4}

works for:

123-678-1234

123 678 1234

(123)-678-1234

+1-(123)-678-1234

1-(123)-678-1234

1 123 678 1234

1 (123) 678 1234