The problem is that (in *ix) the long path "/var/log/../../home/poletti/../../etc/passwd" does not necessarily compact to "/etc/passwd". For example, if "/home/poletti" was a symbolic link to "/drive2/home/poletti", the long path would compact to "/drive2/etc/passwd". That's why canonpath does not eliminate "segment/../" in *ix.

Update: Here's some code that does the trick, ignoring symbolic links:

use File::Spec::Unix ();

sub remove_dot_dot {
   local $_ = $_[0];
   $_ = File::Spec::Unix->canonpath($_);
   1 while s#[^/]+/\.\./##g;
   s#/[^/]+/\.\.$#/#g;
   s#^[^/]+/\.\.$#.#g;
   return $_;
}

[download]

Tests:

printf("%-20s -> %-20s\n", $_, remove_dot_dot($_))
   foreach (qw(
      /foo/..
      /foo/../bar
      foo/..
      foo/../bar
      ..
      ../foo
      ../foo/bar
      foo/bar/../..
      /foo/bar/../..
      /foo/bar/../../moo
      /var/log/../../home/poletti/../../etc/passwd
   ));

__END__
output
======
/foo/..              -> /
/foo/../bar          -> /bar
foo/..               -> .
foo/../bar           -> bar
..                   -> ..
../foo               -> ../foo
../foo/bar           -> ../foo/bar
foo/bar/../..        -> .
/foo/bar/../..       -> /
/foo/bar/../../moo   -> /moo
/var/log/../../home/poletti/../../etc/passwd -> /etc/passwd

[download]

Update2: I got confused and thought ../foo/bar should give bar. Fixed.

In reply to Re: Cleaning up a path by ikegami
in thread Cleaning up a path by polettix

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.