Regular expression to match phone number?

Question

I want to match a phone number that can have letters and an optional hyphen:

• This is valid: 333-WELL
• This is also valid: 4URGENT

In other words, there can be at most one hyphen but if there is no hyphen, there can be at most seven 0-9 or A-Z characters.

I dont know how to do and "if statement" in a regex. Is that even possible?

Answer 1

You seek the alternation operator, indicated with pipe character: |

However, you may need either 7 alternatives (1 for each hyphen location + 1 for no hyphen), or you may require the hyphen between 3rd and 4th character and use 2 alternatives.

One use of alternation operator defines two alternatives, as in:

({3,3}[0-9A-Za-z]-{4,4}[0-9A-Za-z]|{7,7}[0-9A-Za-z])

Answer 2

Thank you Heath Hunnicutt for his alternation operator answer as well as showing me an example.

Based on his advice, here's my answer:

[A-Z0-9]{7}|[A-Z0-9][A-Z0-9-]{7}

Note: I tested my regex here. (Just including this for reference)

Answer 3

I think this should do it:

/^[a-zA-Z0-9]{3}-?[a-zA-Z0-9]{4}$/

It matches 3 letters or numbers followed by an optional hyphen followed by 4 letters or numbers. This one works in ruby. Depending on the regex engine you're using you may need to alter it slightly.

Answer 4

Not sure if this counts, but I'd break it into two regexes:

#!/usr/bin/perl

use strict;
use warnings;

my $text = '333-URGE';

print "Format OK\n" if $text =~ m/^[\dA-Z]{1,6}-?[\dA-Z]{1,6}$/;
print "Length OK\n" if $text =~ m/^(?:[\dA-Z]{7}|[\dA-Z-]{8})$/;

This should avoid accepting multiple dashes, dashes in the wrong place, etc...

Answer 5

Supposing that you want to allow the hyphen to be anywhere, lookarounds will be of use to you. Something like this:

^([A-Z0-9]{7}|(?=^[^-]+-[^-]+$)[A-Z0-9-]{8})$

There are two main parts to this pattern: [A-Z0-9]{7} to match a hyphen-free string and (?=^[^-]+-[^-]+$)[A-Z0-9-]{8} to match a hyphenated string.

The (?=^[^-]+-[^-]+$) will match for any string with a SINGLE hyphen in it (and the hyphen isn't the first or last character), then the [A-Z0-9-]{8} part will count the characters and make sure they are all valid.