How can I modify this regex to require a specific numeric range and also allow an empty string?

Question

I have the following regex:

^([1-9]){3,5}[1-8]$

it works to restrict strings within a certain range, but now I need to change that so that it'll also allow an empty string. How can I do this?

Simon · Accepted Answer · 2013-02-08T12:10:01.480

1

^(([1-9]){3,5}[1-8])?$

Use (?: if you care about the captured groups, if you don't, you can remove the brackets around [1-9]. Brackets around the whole sequence must be kept, though, so the ? quantifier still applies correctly (preceding group zero or one times). So the slightly shorter (maybe more correct) version would be:

^(?:\d{3,5}[1-8])?$

This will return exactly one match, which is the input string as a whole.

edited Feb 08 '13 at 12:10

answered Feb 08 '13 at 12:00

Simon

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Thanks Simon - not sure what you mean about "captured groups" though? – DaveDev Feb 08 '13 at 12:02
Best explained here: http://stackoverflow.com/questions/3512471/non-capturing-group – Simon Feb 08 '13 at 12:05

score 0 · Answer 2 · edited Feb 08 '13 at 12:21

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This should work:

^(|([1-9]){3,5}[1-8])$

edited Feb 08 '13 at 12:21

Spontifixus

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answered Feb 08 '13 at 12:03

fejese

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How can I modify this regex to require a specific numeric range and also allow an empty string?

2 Answers2