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

I got this:

debian:tmp$ cat p.txt
333-444-5555
(333)333-6666
123 456 7890
1234567890
debian:tmp$ egrep '\(?[0-9]{3}[ )-]?[0-9]{3}[ -]?[0-9]{4}' p.txt
333-444-5555
(333)333-6666
123 456 7890
1234567890
debian:tmp$ egrep --version
GNU grep 2.5.3

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debian:tmp$