Isn't glob annoying? (somehow)

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;
  }
[download]

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');
[download]

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

Comment on Isn't glob annoying? (somehow) Select or Download Code

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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'));` [download] cheers, Aldo `__END__ $_=q,just perl,,s, , another ,,s,$, hacker,,print;` [download]	[reply] [d/l] [select]
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, "$_" is used. The "<.c>" op +erator is discussed in more detail in the section on "I/O Operato +rs" in the perlop manpage. ....` [download] As shell expansion, this does what it promises. Here is an example excerpt from my /bin/sh on cygwin: `$ 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` [download] Courage, the Cowardly Dog.	[reply] [d/l] [select]
Re: Re: Isn't glob annoying? (somehow) by PetaMem (Priest) on Aug 02, 2002 at 09:02 UTC
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` [download] contradicts the behaviour in @t3 in my example. Bye PetaMem	[reply] [d/l]
Re: Isn't glob annoying? (somehow) by Abigail-II (Bishop) on Aug 02, 2002 at 10:20 UTC
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 $` [download] Abigail	[reply] [d/l]
Re: Re: Re: Isn't glob annoying? (somehow) by Courage (Parson) on Aug 02, 2002 at 09:26 UTC
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.	[reply] [d/l]


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