in reply to Remove '.' and '..' from a list of filenames

Just watch out, from a security perspective you are also filtering ".\n" and "..\n", which might then sneak by in a file listing when they shouldn't.

-- Randal L. Schwartz, Perl hacker

  • Comment on RE: Remove '.' and '..' from a list of filenames

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RE: RE: Remove '.' and '..' from a list of filenames
by Shendal (Hermit) on Aug 23, 2000 at 00:23 UTC
    I didn't vote you down, but I can see perhaps why someone did. Isn't your reply incorrect? For example, if I write the following:
    @vals = (".","..",".\n","..\n","foo","foo\n","bar","bar\n");

foreach (grep !/^[.]{1,2}$/,@vals) {
  print "$_\n";
}

    [download]
    It spits out:
    foo
foo

bar
bar

    [download]
    ...as I would expect. It filtered out ".\n" and "..\n" just fine. Can you elaborate?
[reply]
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[select]
      ..\n is a valid, albeit very bizarre, file name. This regex would incorrectly filter them out. I believe a more correct solution is to say /\.\.?\z/ \z is a zero width assertion that is true when you are at the actual end of the line as opposed to $, which anchors to the end of the line or possibly \n and the end of the line.

      mikfire

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      A reply falls below the community's threshold of quality. You may see it by logging in.
      Ahh, the problem is that it filters those out when it shouldn't. Sorry, reversed logic strikes. In other words, 
      /^\.$/

      [download]
      matches both dot and dot-newline, and if you were expecting it to match only dot, you could be in for a big shock.

      I've edited the original note to reflect what I meant, not what I said. {grin}

      -- Randal L. Schwartz, Perl hacker

[reply]
[d/l]

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