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Hi, has onyone ever created a regexp to match common credit card formulas? I
have been asked to "validate" some CC#'s we have on file. I do not know the
formulas by which credit cards are generated. All I know is Visa always
starts with 4, Mastercard with 5, and Amex with 3 I think. It would be nice
to have:

$cardtype = param('cardtype');
$cardnumber = param('cardnumber');

if ($cardtype eq "Visa") {
unless ($cardnumber =~ /some valid visa formula/) {
print "It's Good";
} else {
print "It's Bad";
}
}

And so forth. You can find e-commerce websites all over the place that do a
basic check but I don't know the formulas used. At the very least, I would
like to validate the first number as being 4,5,3 etc. and that the scalar is
at least 13 characters long. I do not know how to match just the very first
char of a scalar ... can some one help me with this? EG:

$cardtype = param('cardtype');
$cardnumber = param('cardnumber');

if ($cardtype eq "Visa") {
unless ($cardnumber =~ /first character is 4/ && $cardnumber =~ /at least
13 characters long/) {
print "It's Good";
} else {
print "It's Bad";
}
}

I am very new to writing regexp's and my present knowledge is limited to
validating characters used, not their positions. This was my best guess to
match 4 as first (untested):

unless ($cardnumber =~ /4.*/) { #does not match character length as 13
however
print "It's Good";

} else {
print "It's Bad";
}

Thank you all.
Robert

Robert TV wrote:
> Hi, has onyone ever created a regexp to match common credit card
> formulas? I have been asked to "validate" some CC#'s we have on file.
> I do not know the formulas by which credit cards are generated.

Why aren't you simply using the Business::CreditCard module?

jue

"Robert TV" <> wrote:

> unless ($cardnumber =~ /4.*/) { #does not match character length as 13
> however
> print "It's Good";
>
> } else {
> print "It's Bad";
> }

I just wrote this regexp that seems to correctly match the first number as
4, although i'm not certain if it's the best way:

#!/usr/bin/perl

use CGI qw(:standard);
use CGI::Carp qw(fatalsToBrowser);

$thenumber = "46574656";

if ($thenumber =~ /^[4].*$/) {
print "It's Good";
} else {
print "It's Bad";
}
exit;

Now if I could only figure out how to match against a certain number if
characters (13) in the scalar. Your suggestions are appreciated.

Robert

"Jürgen Exner" <> wrote:

> Why aren't you simply using the Business::CreditCard module?

I do not own my own server or have the ability to install such modules that
are not bundled with Perl5. I have an account with a commercial web hosting
company and a cgi-bin to run my scripts. They will not install custom
modules for me : (

Robert

Robert TV wrote:
> Jürgen Exner wrote:
>> Why aren't you simply using the Business::CreditCard module?
>
> I do not own my own server

Okay.

> or have the ability to install such modules that are not bundled
> with Perl5.

Yes, you have.

> I have an account with a commercial web hosting company and a
> cgi-bin to run my scripts. They will not install custom modules for
> me : (

Have you asked? If they say no, then do it yourself.

perldoc -q "own module"

http://www.mail-archive.com/beginner.../msg59382.html

--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl

"Robert TV" <> writes:
> Hi, has onyone ever created a regexp to match common credit card formulas?

If you were to search for "Credit Card" on http://search.cpan.org/
you'd find Business::CreditCard which claims to

Validate/generate credit card checksums/names

You know, it's kinda rude to ask other people to search for you, when
you can just do the same thing yourself.

> I have been asked to "validate" some CC#'s we have on file.

Do you know what "validate" means? Are you supposed to make sure
they're real credit card numbers, or just that they might be?
Business::CreditCard doesn't really validate cards; it just makes sure
that the credit card number is vaguely plausible.

> I am very new to writing regexp's and my present knowledge is limited to
> validating characters used, not their positions.

You should read 'perldoc perlretut', then. 'perldoc perlrequick' if
you're in a hurry.

> This was my best guess to
> match 4 as first (untested):

Why? You can test it yourself, easily.

> unless ($cardnumber =~ /4.*/) { #does not match character length as 13

That will match a string with a literal '4' in it anywhere.

> however

That will cause a syntax error.

> print "It's Good";
>
> } else {
> print "It's Bad";
> }

Sounds like you've got an idea that regexes can do anything; they can
do a lot, but they're not ideal for everything. Also, sometimes it's
clearer to express yourself not using a regex. For instance, if what
you're concerned with is to find the length of a string, use the
length() function ('perldoc -f length' to find out more).

-=Eric
--
Come to think of it, there are already a million monkeys on a million
typewriters, and Usenet is NOTHING like Shakespeare.
-- Blair Houghton.

> I just wrote this regexp that seems to correctly match the first number as
> 4, although i'm not certain if it's the best way:
>
> #!/usr/bin/perl
>
> use CGI qw(:standard);
> use CGI::Carp qw(fatalsToBrowser);
>
> $thenumber = "46574656";
>
> if ($thenumber =~ /^[4].*$/) {
> print "It's Good";
> } else {
> print "It's Bad";
> }
> exit;
>
> Now if I could only figure out how to match against a certain number if
> characters (13) in the scalar. Your suggestions are appreciated.
>

>At the very least, I would
>like to validate the first number as being 4,5,3 etc. and that the scalar
is
>at least 13 characters long. I do not know how to match just the very first
>char of a scalar ... can some one help me with this? EG:
>

Instead of the * quantifier, you could use {12,} who will match 12 or more
charaters (plus the leading 4 = 13).

/^4.{12,}/ #but that would match much more than digits

Using character classes might be the answer

/^4[\d]{12,}/ # should match a string that begin with 4 plus 12 digit

DAE

Robert TV wrote:
> "Jürgen Exner" <> wrote:
>
>> Why aren't you simply using the Business::CreditCard module?
>
> I do not own my own server or have the ability to install such
> modules that are not bundled with Perl5.

Option 1: perldoc -q module: "How do I keep my own module/library
directory?"
Option 2: instead of reinventing the wheel just copy the (relevant subset
of) code from that module into your own program

jue

"Gunnar Hjalmarsson" <> wrote

> Have you asked? If they say no, then do it yourself.
>
> perldoc -q "own module"
>
> http://www.mail-archive.com/beginner.../msg59382.html

Thank you Gunnar, that tutorial helped me install a .pm on the server and it
works great.

Robert

"Eric Schwartz" <> wrote

> You know, it's kinda rude to ask other people to search for you, when
> you can just do the same thing yourself.

I didn't want people to do my work for me, I really didn't know where to
start with my research. I know very little about CPAN but am starting to
learn its a good resource.

> Do you know what "validate" means? Are you supposed to make sure
> they're real credit card numbers, or just that they might be?
> Business::CreditCard doesn't really validate cards; it just makes sure
> that the credit card number is vaguely plausible.

I now have CPAN's CC validity module working.

> You should read 'perldoc perlretut', then. 'perldoc perlrequick' if
> you're in a hurry.

I'll have a look ty.
R