Solved

# Perl script to mask a credit card number

Posted on 2003-12-02
1,283 Views
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!
0
Question by:EschbacherG
• 3
• 2
• 2
• +2

LVL 20

Accepted Solution

jmcg earned 81 total points
(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.
0

LVL 2

Author Comment

What if there are no spaces in the cardnumber?

like  123412324123241234?  Can i just remove your spaces from your regular expression?
0

LVL 51

Assisted Solution

ahoffmann earned 20 total points
\$credit_card_number=~s((\d{4}( ?)){3})((x x 4) x 3)e;
0

LVL 20

Expert Comment

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.
0

LVL 1

Expert Comment

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; <----
0

LVL 20

Expert Comment

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.
0

LVL 1

Expert Comment

thanks, I owe you some points :).

sorry to use your question space EschbacherG.
0

LVL 51

Expert Comment

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 ..
0

LVL 2

Author Comment

Thank you both very much for your quick answers.   In the end, I went with jmcg's suggestion.
0

Expert Comment

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?
0

## Featured Post

### Suggested Solutions

I've just discovered very important differences between Windows an Unix formats in Perl,at least 5.xx.. MOST IMPORTANT: Use Unix file format while saving Your script. otherwise it will have ^M s or smth likely weird in the EOL, Then DO NOT use m…
On Microsoft Windows, if  when you click or type the name of a .pl file, you get an error "is not recognized as an internal or external command, operable program or batch file", then this means you do not have the .pl file extension associated with …
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
Polish reports in Access so they look terrific. Take yourself to another level. Equations, Back Color, Alternate Back Color. Write easy VBA Code. Tighten space to use less pages. Launch report from a menu, considering criteria only when it is filled…