regular expression limit hex number length by using OR

Question

I want to limit the length of hex number to 4 OR 8. For example:

0x0001 is valid (4 hex numbers)

0x0001001F is valid (8 hex numbers)

0x00012 is invalid (5 hex numbers)

I can validate a hex number with length of n (n is 4 or 8) by using

Regex.IsMatch("0x0001", "^0x[0-9a-fA-F][{n}$");

How to achieve this OR operation, say either 4 or 8, not from 4 to 8?

It is not "number" but "hex digit" than you mean (e.g. `0x00012` is one single number written with four hex digits). — Basile Starynkevitch, Nov 24 '11 at 11:32

score 4 · Accepted Answer · answered Nov 24 '11 at 11:31

4

"Or" is represented by | in regex. Your regex would therefore look like

0x([0-9a-fA-F]{4}|[0-9a-fA-F]{8})

Another way would be to make the last four digits optional using ?. This would lead to

0x[0-9a-fA-F]{4}([0-9a-fA-F]{4})?

answered Nov 24 '11 at 11:31

Jens

1

You could make it shorter by matching the group of four digits 1-2 times: `0x([0-9a-fA-F]{4}){1,2}` – Herohtar Aug 07 '19 at 19:47

1 Answers1