PetaMem has asked for the wisdom of the Perl Monks concerning the following question:

Hello brothers,

I've stumbled across the following code: 

  my $mask    = shift;
  my @folders    = glob("$mask");

  if (scalar(@folders) == 0) {
    return undef;
  }

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It seems unelegant and unrobust to me, so I investigated a little bit further. To my surprise I found a strange behaviour of glob, when a glob is given that does not match but that does not contain wildcards also. Given the folowing examples: 
@t1 = glob('*1');
@t2 = glob('1');
@t3 = glob('file2');
@t4 = glob('*3');

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assume you have the files file1 and file2 in the directory glob is searching, the returns are 'file1' for @t1, '1' for @t2, 'file2' for @t3 and the empty list for @t4.

The behaviour for @t2 is what seems odd/annoying. In my opinion it should be empty, as the current semantics make it indistinguishable from the @t3 case - which is correct imho.

Please tell me, that I've found a bug that is soon to be fixed... :-}

Bye
 PetaMem

Replies are listed 'Best First'.
Re: Isn't glob annoying? (somehow)
by dada (Chaplain) on Aug 02, 2002 at 11:07 UTC
    as already pointed out, glob isn't strictly supposed to find existing files, but rather to do filenames expansion. however, you can do this to get the result you expect: 

    @t1 = grep(-e, glob('*1'));
@t2 = grep(-e, glob('1'));
@t3 = grep(-e, glob('file2'));
@t4 = grep(-e, glob('*3'));

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    cheers,
    Aldo 

    __END__
$_=q,just perl,,s, , another ,,s,$, hacker,,print;

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Re: Isn't glob annoying? (somehow)
by Courage (Parson) on Aug 02, 2002 at 08:49 UTC
    perldoc -f glob says: 
        glob EXPR
    glob    Returns the value of EXPR with filename expansions such as
+ the
            standard Unix shell /bin/csh would do. This is the interna
+l
            function implementing the "<*.c>" operator, but you can us
+e it
            directly. If EXPR is omitted, "$_" is used. The "<*.c>" op
+erator
            is discussed in more detail in the section on "I/O Operato
+rs" in
            the perlop manpage.
....

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    As shell expansion, this does what it promises. Here is an example excerpt from my /bin/sh on cygwin: 
    $ echo *
Desktop Mail _viminfo building-gcc-for-mips.txt car.pic gcc gdbtk.ini 
+kbuildsycoca.exe.stackdump kikbd.exe.stackdump parrot pwin32 x0 x1 xx

Administrator@RTC ~
$ echo *jd
*jd

Administrator@RTC ~
$ echo dwq
dwq

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    Courage, the Cowardly Dog.

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[d/l]
[select]
      First off, my camel book has a slightly different text ("such as a shell would do"), and if I look at your results, then this 
      $ echo *jd
*jd

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      contradicts the behaviour in @t3 in my example.

      Bye
       PetaMem

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[d/l]
        It's a BSD glob. The original BSD shell is the csh, not the Bourne shell or some derivate of that. 
            $ ls *1
    *1 not found
    $ csh
    % ls *1
    No match.
    % exit
    $

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        Abigail
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[d/l]
        I also noticed that it contradicts to @t3 example, but command next to it explains glob('1') behaviour.

        And yes, I agree that glob's behaviour is somewhat tricky, or even more to say, weird.

        Courage, the Cowardly Dog.

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