# Regex help **URL:** \ **Category:** Ruby\ **Created:** [January 11, 2010, 1:39pm UTC](https://www.ruby-forum.com/t/regex-help/181397 "2010-01-11T13:39:37Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![chrislo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/5e9695/32.png) [@chrislo](https://www.ruby-forum.com/u/chrislo)\ **Post date:** [January 11, 2010, 1:39pm UTC](https://www.ruby-forum.com/t/regex-help/181397/1 "2010-01-11T13:39:37Z")
Hi I want to test a string for three properties: 1. It is exactly 9 characters long. 2. Character number 5 is a comma (’,’). 3. The other characters are either numbers 0-9 or letters a-f. I have been able to do this by a combination of strings methods for 1) and 2), and using a regex match on the string (stripped of the comma) with the following code: myString =~ /([^a-f0-9])/ If possible I would like to simplify this by using a more advanced regex match to check all three properties at one time. If this is possible, perhaps one of you regex wizards out there could show me how? 🙂 Best regards, Chris ---
**Author:** ![chrislo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/5e9695/32.png) [@chrislo](https://www.ruby-forum.com/u/chrislo)\ **Post date:** [January 11, 2010, 1:51pm UTC](https://www.ruby-forum.com/t/regex-help/181397/2 "2010-01-11T13:51:21Z")
On Monday 11 January 2010, Chris L. wrote: > | > |If possible I would like to simplify this by using a more advanced regex > |match to check all three properties at one time. If this is possible, > |perhaps one of you regex wizards out there could show me how? 🙂 > | > |Best regards, > |Chris You could do this with a regexp which matches the following: - the beginning of the string - four characters of type a-f or digits - a comma - four characters of type a-f or digits - the end of the string The regexp is: /^[a-f\d]{4},[a-f\d]{4}$/ Note that your string can contain newlines, you must replace ^ and $ with \A and \Z respectively. I hope this helps Stefano ---
**Author:** ![chrislo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/5e9695/32.png) [@chrislo](https://www.ruby-forum.com/u/chrislo)\ **Post date:** [January 11, 2010, 1:56pm UTC](https://www.ruby-forum.com/t/regex-help/181397/3 "2010-01-11T13:56:02Z")
On Mon, Jan 11, 2010 at 1:39 PM, Chris L. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > If possible I would like to simplify this by using a more advanced regex > match to check all three properties at one time. If this is possible, > perhaps one of you regex wizards out there could show me how? 🙂 irb(main):006:0\> re = /\A[a-f0-9]{4},[a-f0-9]{4}\z/ =\> /\A[a-f0-9]{4},[a-f0-9]{4}\z/ irb(main):007:0\> “abcd,4f2ddf” =~ re =\> nil irb(main):008:0\> “abcd,4f32” =~ re =\> 0 Hope this helps, Jesus. ---
**Author:** ![chrislo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/5e9695/32.png) [@chrislo](https://www.ruby-forum.com/u/chrislo)\ **Post date:** [January 11, 2010, 1:58pm UTC](https://www.ruby-forum.com/t/regex-help/181397/4 "2010-01-11T13:58:58Z")
2010/1/11 Stefano C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > > |myString =~ /([^a-f0-9])/ > > - four characters of type a-f or digits > - a comma > - four characters of type a-f or digits > - the end of the string > > The regexp is: > /^[a-f\d]{4},[a-f\d]{4}$/ > > Note that your string can contain newlines, you must replace ^ and $ with \A > and \Z respectively. I believe this should rather be \z because \Z allows for a follwing newline. So that would be /\A[a-f\d]{4},[a-f\d]{4}\z/ see [サービス終了のお知らせ](http://www.geocities.jp/kosako3/oniguruma/doc/RE.txt) Kind regards robert ---
**Author:** ![chrislo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/5e9695/32.png) [@chrislo](https://www.ruby-forum.com/u/chrislo)\ **Post date:** [January 11, 2010, 2:03pm UTC](https://www.ruby-forum.com/t/regex-help/181397/5 "2010-01-11T14:03:39Z")
On Monday 11 January 2010, Robert K. wrote: > |\> Note that your string can contain newlines, you must replace ^ and $ > |\> with \A and \Z respectively. > | > |I believe this should rather be \z because \Z allows for a follwing > |newline. So that would be > | > |/\A[a-f\d]{4},[a-f\d]{4}\z/ You’re right. Stefano ---
**Author:** ![chrislo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/5e9695/32.png) [@chrislo](https://www.ruby-forum.com/u/chrislo)\ **Post date:** [January 11, 2010, 2:45pm UTC](https://www.ruby-forum.com/t/regex-help/181397/6 "2010-01-11T14:45:48Z")
On Jan 11, 5:57 am, Robert K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > On Monday 11 January 2010, Chris L. wrote: > > > > > |I want to test a string for three properties: > > > |1) It is exactly 9 characters long. > > > |2) Character number 5 is a comma (‘,’). > > > |3) The other characters are either numbers 0-9 or letters a-f. > > > /\A[a-f\d]{4},[a-f\d]{4}\z/ Slightly more terse: /\A\h{4},\h{4}\z/ …where \h is a hexadecimal character [0-9a-fA-F] (assuming upper- case a-f is fine). ---
**Author:** ![chrislo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/5e9695/32.png) [@chrislo](https://www.ruby-forum.com/u/chrislo)\ **Post date:** [January 11, 2010, 3:44pm UTC](https://www.ruby-forum.com/t/regex-help/181397/7 "2010-01-11T15:44:29Z")
Gavin K. wrote: > Slightly more terse: > /\A\h{4},\h{4}\z/ > …where \h is a hexadecimal character [0-9a-fA-F] (assuming upper- > case a-f is fine). Alright, thanks guys for excellent insight and help! I especially like this last suggestion which is both compact and easy to comprehend. ---
**Author:** ![chrislo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/5e9695/32.png) [@chrislo](https://www.ruby-forum.com/u/chrislo)\ **Post date:** [January 11, 2010, 4:35pm UTC](https://www.ruby-forum.com/t/regex-help/181397/8 "2010-01-11T16:35:18Z")
At 2010-01-11 07:57AM, “Robert K.” wrote: > /\A[a-f\d]{4},[a-f\d]{4}\z/ > ON the other hand, \Z saves you a .chomp > see [サービス終了のお知らせ](http://www.geocities.jp/kosako3/oniguruma/doc/RE.txt) I’d love to see that kind of documentation in the core Ruby docs.