regex string of 0 or 8 chars

Question

How can I write a regular expression that would accept only alphanumeric chars and the string's length be 0 or 8? What i managed to do until now is

^[a-zA-Z0-9]{0-8}$

Which verifies that my string contains only alphanumeric chars but still allows any string of length between 0 and 8. Is there any way to separate it in either {0} || {8} (in same regex)

possible duplicate of [Reference - What does this regex mean?](http://stackoverflow.com/questions/22937618/reference-what-does-this-regex-mean) — ivan_pozdeev, Feb 25 '15 at 11:15
did you want to allow `foobarba`? since it contains alphabetic characters — Avinash Raj, Feb 25 '15 at 11:17

score 2 · Accepted Answer · answered Feb 25 '15 at 11:16

2

^(?:[a-zA-Z0-9]{8}|)$

Try this for only 0 or 8.

See demo.

https://regex101.com/r/wU7sQ0/9

answered Feb 25 '15 at 11:16

vks

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Thanks, exactly what i was needing. I will accept the answer in 10 mins (when I will be allowed) – next_user Feb 25 '15 at 11:20
1

or `^(?:[a-zA-Z0-9]{8})?$` – Avinash Raj Feb 25 '15 at 11:21
there's no need for `?:` operator if you use the anchors. Just `^([a-zA-Z0-9]{8}|)$` or `^([a-zA-Z0-9]{8})?$` – Luis Colorado Feb 26 '15 at 12:03

regex string of 0 or 8 chars

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