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Perl script to mask a credit card number

Posted on 2003-12-02
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Last Modified: 2012-08-14
Here's the basic idea:  given a 16 digit credit card number, I want to replace the first 12 digits with x's.

Example:  1223 1223 1234 2345  would become   xxxx xxxx xxxx 2345

I'm using ActiveState Perl.


Thanks for any assistance!
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Question by:EschbacherG
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jmcg earned 81 total points
ID: 9861641
(my $credit_card_number_masked = $credit_card_number) =~ s/.*(\d{4})$/xxxx xxxx xxxx $1/;

This just picks off and preseres the last four digits, disregarding whatever comes before.
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by:EschbacherG
ID: 9861880
What if there are no spaces in the cardnumber?

like  123412324123241234?  Can i just remove your spaces from your regular expression?
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by:ahoffmann
ahoffmann earned 20 total points
ID: 9862716
$credit_card_number=~s((\d{4}( ?)){3})((x x 4) x 3)e;
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by:jmcg
ID: 9863132
If preserving the spaces (or lack of spaces) is important, you'll have to do something more like what ahoffman is showing you. If you want the x-ed-out credit card number to look a particular way, however, you're better off using my approach.
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by:josephfluckiger
ID: 9863934
Hope you don't mind me asking a question here, but what does the "e" at the end of the expression do?

$credit_card_number=~s((\d{4}( ?)){3})((x x 4) x 3)e; <----
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by:jmcg
ID: 9864234
An "e" modifier on a substitution indicates that the right hand side of the substitution is to be interpreted as a perl expression rather than as a double-quoted string literal (well, nearly). You can even put extra "e"s there to get multiple levels of expression interpretation, but I've never seen this usefully done more than two levels deep.
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by:josephfluckiger
ID: 9864543
thanks, I owe you some points :).

sorry to use your question space EschbacherG.
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by:ahoffmann
ID: 9865720
well, my suggestion is not perfect, and to be improved in many ways (as jmcg's too:), but it answers the question
KISS - keep it stupid simple  ;-)

josephfluckiger, probably you replace
  x x 4
in my suggestion by
  X x 4
to understand what happens
  print "X" x 4
characters are just characters, and some have special meaning in special context ..
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by:EschbacherG
ID: 9867045
Thank you both very much for your quick answers.   In the end, I went with jmcg's suggestion.
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Expert Comment

by:joneoytk
ID: 10721194
so what if the input from keyboard and i dont want it to show on the screen.does this command (my $credit_card_number_masked = $credit_card_number) =~ s/.*(\d{4})$/xxxx xxxx xxxx $1/;
work on my concept too?
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