This question is answered in the IAQ, under the question "How do I decrypt a string that I encrypted with crypt()?" (since crypt generates "UNIX style passwords", usually). To quote their answer: 


        sub decrypt {
          my $c = shift;
          my @c = (0) x 8;
          for (;;) {
            my $i = 0;
            my $s = join '', map chr, @c;
            return $s if crypt($s, $c) eq $c;
            $c[$i]=0, $i++ while $c[$i] == 255;
            return undef if $i > 7;
            $c[$i]++;
          }
        }

[download]

(For the humor impaired, the IAQ is not serious; quoth crypt's docs: "Note that "crypt" is intended to be a one-way function... There is no (known) corresponding decrypt function." This functions attempts to brute force the crypt'd string and thus is extremely slow.)

In reply to Re: Decrypt UNIX password by wog
in thread Decrypt UNIX password by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.