# Reg: regular expression **URL:** \ **Category:** Rails\ **Created:** [March 20, 2007, 5:57am UTC](https://www.ruby-forum.com/t/reg-regular-expression/89401 "2007-03-20T05:57:43Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![shiva\_98](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@shiva\_98](https://www.ruby-forum.com/u/shiva_98)\ **Post date:** [March 20, 2007, 5:57am UTC](https://www.ruby-forum.com/t/reg-regular-expression/89401/1 "2007-03-20T05:57:43Z")
how to validate using regular expression using 1.name should be alpha numeric 2.min 5 characters and max 15 3.“two alphabets followed by a number” format not allowed in the beginning .if any one have solution.pls send me ---
**Author:** ![shiva\_98](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@shiva\_98](https://www.ruby-forum.com/u/shiva_98)\ **Post date:** [March 20, 2007, 6:19am UTC](https://www.ruby-forum.com/t/reg-regular-expression/89401/2 "2007-03-20T06:19:54Z")
> 1.name should be alpha numeric > 2.min 5 characters and max 15 > 3.“two alphabets followed by a number” format not allowed in the > beginning .if any one have solution.pls send me Completely untested. (Straight from brain to keyboard, so you will have to debug.) Not sure I understand #3 correctly, but if you _want_ to match two letters followed by one or more alpha-numerics, something like this should work, but again, untested… validates\_length\_of :whatever, :within =\> 5…15, :on =\> :create, :message =\> “must be between 5 and 15 characters long” validates\_format\_of :whatever, :with =\> %r{\A[a-zA-Z]{2}\w+ \Z}, :message =\> “must be blah blah blah.” Good luck. Preston ---
**Author:** ![shiva\_98](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@shiva\_98](https://www.ruby-forum.com/u/shiva_98)\ **Post date:** [March 20, 2007, 6:37am UTC](https://www.ruby-forum.com/t/reg-regular-expression/89401/3 "2007-03-20T06:37:40Z")
thans buddy