RegEx for a license plate

Question

I have to validate a text value with RegEx for the following possible types of expressions: (must be 8 characters with 2 hyphens and 6 alphanumeric characters.)

aa-99-99
99-23-bd
02-xx-04
ab-99-cz
sc-xd-49
99-xav-4
48-xyz-09
9-abc-01
xs-899-x
sss-99-x

I tried the following regex pattern but it didn't work:

/^(\d{1,3})-(\d{1,3})-(\d{1,3})$/

How is `48-xyz-09` 8 characters? – Rotem Jul 05 '19 at 18:59 — Rotem, Jul 05 '19 at 18:59
Many of these are not 8 characters. – Matthew Anderson Jul 05 '19 at 19:04 — Matthew Anderson, Jul 05 '19 at 19:04

41686d6564 stands w. Palestine · Answer 1 · 2019-07-05T19:12:36.543

4

Update after OP's clarification:

If you'd like to only allow letter or numbers in each block, you may use:

^(?=.{8}$)(?:(?:[a-z]+|[0-9]+)(?:-|$)){3}

Demo.

If you also want to make sure the string contains both letters and numbers, you may use the following instead:

^(?=.{8}$)(?=.*[a-z])(?=.*[0-9])(?:(?:[a-z]+|[0-9]+)(?:-|$)){3}

Demo.

Original answer:

If I understand your requirements correctly, you may use something like this:

/^(?=.{8}$)[a-z0-9]{1,3}-[a-z0-9]{1,3}-[a-z0-9]{1,3}$/

Demo.

Breakdown:

^             # The beginning of the string.
(?=.{8}$)     # A positive Lookahead to limit the length of the string to exactly 8 chars.
[a-z0-9]{1,3} # One to three alphanumeric (English) characters.
-             # Matches the character "-" literally.
$             # The end of the string.

Update:

If you want to avoid repeating the [a-z0-9]{1,3} part, you may use something like this:

^(?=.{8}$)(?:[a-z0-9]{1,3}(?:-|$)){3}

...but the pattern will not be as easy to read so I would stick with the first one.

References:

edited Jul 05 '19 at 19:12

answered Jul 05 '19 at 18:33

41686d6564 stands w. Palestine

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@ahmed abdelhameed: It worked but there is some gap i.e it should have combination of atleast one set of numbers or alphabets i.e 89-19-ab and not 99-99-99 or aa-ab-aa. How we can use ÖR? – sai Jul 05 '19 at 18:40
This is a great answer and great work, but it doesn't answer OP's question. Here are the issues. 1) OP wants letters and numbers to be in blocks so `44-aa-bb` would work, but `a7-b8-c9` would not. 2) OP appears to want some combination of letters and numbers, so you cannot have a string such as `ab-cd-ef` or `12-34-56`. – Matthew Anderson Jul 05 '19 at 18:57
Good explaination Ahmed – sai Jul 05 '19 at 18:57
The combination of 10-b1-c2 is not allowed . aa-bb-01 or 10-11-ac similar can be allowed – sai Jul 05 '19 at 18:59
@sai so neither of the answers satisfy this, why did you accept one? – Rotem Jul 05 '19 at 19:00
@MatthewAnderson That wasn't clear at the beginning. Updated the answer. – 41686d6564 stands w. Palestine Jul 05 '19 at 19:05
@Rotem : Sorry I missed some scenarios . It seems you have tested a lot :) – sai Jul 05 '19 at 19:05
It matches `11-11-11` yet. – revo Jul 05 '19 at 19:06
@revo I'm still not sure if the OP wants to reject that but updated the answer anyway. – 41686d6564 stands w. Palestine Jul 05 '19 at 19:13
@ahmed abdehameed; Its working but (min 1 to max3)-(min 1 to max3)-(min1 to max2) The last set should have max 2 only first two set may contain maximum 3 i.e 212-01-a, aa-200-c are valid but not 0-20-aaa – sai Jul 05 '19 at 19:24
To ensure the RegEx string contains both letters and numbers, it would be simpler to use the positive lookahead `(?=.*\d)` instead of the one that you use `(?=.*[a-z])(?=.*[0-9])`. – Matthew Anderson Jul 05 '19 at 19:26
@sai Please remember to include all your rules in the question from the beginning. Anyway, you may use [`^(?=.{8}$)(?=.*[a-z])(?=.*[0-9])(?:(?:[a-z]{1,3}|[0-9]{1,3})-){2}(?:[a-z]{1,2}|[0-9]{1,2})$`](https://regex101.com/r/WgkYvQ/1) – 41686d6564 stands w. Palestine Jul 05 '19 at 19:31
@MatthewAnderson How does `(?=.*\d)` enforce containing a letter? – 41686d6564 stands w. Palestine Jul 05 '19 at 19:32
It does not enforce containing a letter. My mistake. – Matthew Anderson Jul 06 '19 at 03:38

score 2 · Answer 2 · answered Jul 05 '19 at 18:50

2

Try the following regex with m flag on:

^(?=.{8}$)[^\W_]+(?:-[^\W_]+)+$

If you need to force a combination of both digits and letters use this:

^(?=.{8}$)(?![\d-]+$|[a-z-]+$)[^\W_]+(?:-[^\W_]+)+$

See live demo here

answered Jul 05 '19 at 18:50

revo

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It worked. Can you explain the regex how it checks the combinations – sai Jul 05 '19 at 18:57
Currently it seems that you have to modify your requirements to express what you really need otherwise we can't help you very well. – revo Jul 05 '19 at 19:04
No change in requirement, I'll give more clarity if you dint really understand. – sai Jul 05 '19 at 19:14
8 digit which should have two minus i.e (min 1 to max3)-(min 1 to max3)-(min1 to max2) and the combination should be at least one alphabet or number combination not all alphabets or numbers i.e 00-aa-10 is valid , 00-00-00 , aa-aa-aa is not valid – sai Jul 05 '19 at 19:17
Your question doesn't include these or whatever else you may want to add later. Please edit your question. – revo Jul 05 '19 at 19:23

RegEx for a license plate

2 Answers2

Update after OP's clarification:

Original answer:

References: