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Hi Monks,

a colleague of mine came to me with a question on a special regex which has to decide whether a given pw is valid or not. The pw has to suffice the following restrictions:

it's length has to be within 5-8 chars
at least one lower-char, one upper-char and one number has to occur

I agreed to him that this requirement isn't trivial. But on the other side I told him that i could imagine a really short solution. Perhaps i leaned out of the window a bit too wide, because after a little fiddling i got this:

#!/usr/bin/perl -w

# vim: set tabstop=3

use strict;

while (<DATA>)
{
    chomp;
    print "\n$_\n";
    length() < 5 && do { print "too short\n";    next };
    length() > 8 && do { print "too long\n";     next };
    m#
        ^
        \w*[a-z]\w*[A-Z]\w*[0-9]\w*|
        \w*[a-z]\w*[0-9]\w*[A-Z]\w*|
        \w*[A-Z]\w*[a-z]\w*[0-9]\w*|
        \w*[A-Z]\w*[0-9]\w*[a-z]\w*|
        \w*[0-9]\w*[A-Z]\w*[a-z]\w*|
        \w*[0-9]\w*[a-z]\w*[A-Z]\w*
        $
    #x     
        ? print "valid\n"
        : print "invalid (Input must have at least one lowercase-, " .
                  "one uppercase-Char and one Number! (f.i.: \'12Three
+\')\n";

}
__DATA__
1245Za78
1245Za7b8
45a7b8
a78Z
12Three
kMdlOz
6KYX
diImMU1Y
ZNw4uWSht
jDqvSN
qVRR
le2WTQv
us1j3SerC
OZv0LtSJ
9qyscg
LbX7o74
80TeRHq
7YIiXnEV8
e1Yctl9
8iGoc
R87MeDCFz
ziTnlk
cziP
[download]

This solution is quite good but appears a little bulky to me. Especially a more compact regex would be nice. Perhaps the length-validation could be made within the regex too.

I wonder who has THE solution which combines shortness and elegance in a tremendous way ;)

regards, tos

_{janitored by ybiC: Balanced <readmore> tags, minor format cleanup for legibility}

In reply to regex elegance contest - validate a pw by tos

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