Regular Expressions match exactly 7 or 9 digits

Question

My reg ex skills are almost zero and I am trying to match a field to have exactly 7 or 9 numbers (not between 7 or 9 so no 8 numbers is not valid).

I have tried (don't laugh)

/^([0-9]{7} | [0-9]{9})

and

/^([0-9]{7 | 9})

if someone could help and explain the answer that would be much appreciated.

I assume (maybe incorrectly) that is does not matter what (programming) language I am using

Thanks

score 26 · Accepted Answer · edited Aug 03 '12 at 14:49

26

/^\d{7}(?:\d{2})?$/

\d is modern regex shorthand for [0-9], using (?: prevents a group capture you don't want or need from happening.

edited Aug 03 '12 at 14:49

Andrei Bârsan

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answered Aug 03 '12 at 14:44

chaos

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old answer, I know, but why wouldn't this work? `/^\d{7}(\d{2})?$/` I understand it would create a group capture - but does that matter in this instance? I wonder if the reason is memory related? Be gentle - regex is not my forté. – calipoop Mar 28 '18 at 18:10
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@calipoop: it will work fine, it's just a poor habit to request behavior (group capture) that you don't need. – chaos Apr 10 '18 at 17:37
This answer would not catch 7 zeros like 0000000 – Sani Yusuf Jul 23 '18 at 20:14
@SaniYusuf: Of course it does. Maybe try it first. Why did you think that? – chaos Jul 25 '18 at 20:03
I should have clarified. It won't catch on an input where type is number since 00000 still evaluates as 0. Changing to type text solved it. – Sani Yusuf Jul 26 '18 at 01:11

score 10 · Answer 2 · answered Aug 03 '12 at 14:47

10

Your first approach works. Just leave out the blanks, add a $ to match the string end and the trailing slash delimiter. You also could replace [0-9] with the shortcut \d:

/^(\d{7}|\d{9})$/

answered Aug 03 '12 at 14:47

Bergi

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score 6 · Answer 3 · answered Aug 03 '12 at 14:40

6

Seven or nine digits is seven digits optionally followed by two more digits:

[0-9]{7}([0-9]{2})?

answered Aug 03 '12 at 14:40

Fred Foo

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You have to anchor the expression. – Felix Kling Aug 03 '12 at 14:41
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Depends on where they use it. Not for Java's `Pattern.matches()` for example. – Joey Aug 03 '12 at 14:42

score 3 · Answer 4 · answered Aug 03 '12 at 14:41

3

use this regex ^\d{7}(\d{2})?$

answered Aug 03 '12 at 14:41

burning_LEGION

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score 0 · Answer 5 · edited May 23 '17 at 10:30

0

This is probably easier done in the programming lanuage that you're using, but it can be achieved in regex as well. Take a look at this link : Regular expression to limit number of characters to 10

edited May 23 '17 at 10:30

Community

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answered Aug 03 '12 at 14:42

mlishn

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score 0 · Answer 6 · answered Aug 03 '12 at 14:43

0

Your first one will work if you just remove the spaces (and optionnaly the parenthesis).

answered Aug 03 '12 at 14:43

kgautron

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Regular Expressions match exactly 7 or 9 digits

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