# Reg exp question

**URL:** <https://www.ruby-forum.com/t/reg-exp-question/127186>\
**Category:** Ruby\
**Created:** [January 25, 2008, 11:02pm UTC](https://www.ruby-forum.com/t/reg-exp-question/127186 "2008-01-25T23:02:23Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![laredotornado](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/9dc877/32.png) [@laredotornado](https://www.ruby-forum.com/u/laredotornado)\
**Post date:** [January 25, 2008, 11:02pm UTC](https://www.ruby-forum.com/t/reg-exp-question/127186/1 "2008-01-25T23:02:23Z")

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Hi,

If I have a variable @fax, how can I apply a regular expression to the  
variable such that all non-numeric characters are removed? You can  
assume the fax number is of a valid US format.

Thanks, - Dave

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**Author:** ![laredotornado](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/9dc877/32.png) [@laredotornado](https://www.ruby-forum.com/u/laredotornado)\
**Post date:** [January 25, 2008, 11:32pm UTC](https://www.ruby-forum.com/t/reg-exp-question/127186/2 "2008-01-25T23:32:55Z")

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laredotornado wrote:

> If I have a variable @fax, how can I apply a regular expression to the  
> variable such that all non-numeric characters are removed? You can  
> assume the fax number is of a valid US format.

str = ‘1234abc5d6e7f8ghi’

result = str.gsub(/\D/, “”)  
puts result

–output:–  
12345678

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<div class="post-metadata">

**Author:** ![laredotornado](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/9dc877/32.png) [@laredotornado](https://www.ruby-forum.com/u/laredotornado)\
**Post date:** [January 25, 2008, 11:35pm UTC](https://www.ruby-forum.com/t/reg-exp-question/127186/3 "2008-01-25T23:35:06Z")

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7stud – wrote:

> result = str.gsub(/\D/, “”)

\D is the symbol for any character except a digit, which is shorthand  
for [^0-9].