In #perlhelp on EFnet, someone said: 

14:01 < mauke> Is this a feature? mkdir tmp; cd tmp; touch 'echo Hello
+, world |'; perl -pe1 *
14:03 < mauke> Even better: touch 'rm -rf `echo \\\\57` |'; perl -pe1 
+*

[download]
The first one is safe to run. It prints "Hello, world". The second one is on most systems not safe to run. It deletes everything it can, starting at /.

This feature is documented in perlop:

You can even set them to pipe commands. For example, this automatically filters compressed arguments through gzip:            @ARGV = map { /\.(gz|Z)$/ ? "gzip -dc < $_ |" : $_ } @ARGV;

So all code using the filehandle ARGV (this includes oneliners using -n or -p) is unsafe if used with shell globs.

Unfortunately, -p and -n are used in a LOT of places. Often in scripts that cron starts once a day. Often running as root. I found 5 root holes on my server system.

The fix is easy, but a lot of typing, which isn't handy for oneliners. You should open the files explicitly, using 3-argument open.

Too bad this is a feature. If it weren't documented, I'd say it's a bug and a very scary one too.

:(

Juerd # { site => 'juerd.nl', plp_site => 'plp.juerd.nl', do_not_use => 'spamtrap' }

In reply to Dangerous diamonds! by Juerd

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.