When using glob in a scalar context, you must loop until it returns undef. Compare

use strict;
use warnings;

use File::DosGlob 'glob';

$| = 1;

for (1..2) {
   my $glob = glob($0);
   print($glob, "\n");
}

__END__
script.pl
Use of uninitialized value in print at script.pl line 11.
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with

use strict;
use warnings;

use File::DosGlob 'glob';

$| = 1;

for (1..2) {
   while (defined(my $glob = glob($0))) {
      print($glob, "\n");
   }
}

__END__
script.pl
script.pl
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That said, I'm not sure why you're using glob at all if you only look at the first element. Why not just do unless ( -f  $template_file )?

That said, I'm not sure why you're using glob at all if you only look at the first element. Why not just do unless ( -f $template_file )?

I have a list of files that I want to ensure are actually files (the user will be feeding in filenames via a configuration file and I don't want the program to go further if said file(s) don't exist). I'm using glob in case the absolute path names contain a space character somewhere.

The thing that's bothering me about this is "Why does glob give me a valid answer for the first item in my list, even when I'm using it in scalar context, and not the second?" Is it set in stone somehow, like m/$abc/o is set to only optimize the first interpretation you ask of it? Because in my example, when I use a different instance of glob (i.e. the second foreach loop/block) against the "second" filename, it kicks it out just fine (and then fails on the "previously okay" first value). In DWIM-land, I'd think that each invocation of glob, even within a foreach loop, would be independent of the last.

Though as I said before, I can move ahead with answers that work, and the slice/[0] suggestion works. :-)

I'm using glob in case the absolute path names contain a space character somewhere.

How does glob help you with path names that have spaces? glob accepts a file spec (i.e. something with *) and returns all matching files. It's used to allow the user to specify multiple files at once. However, since you're only interested in one file, it makes no sense to accept file specs or to use glob.

-f works with spaces, whether you've passed the value through glob or not.

The thing that's bothering me about this is "Why does glob give me a valid answer for the first item in my list, even when I'm using it in scalar context, and not the second?"

When glob is called in a scalar context, it still returns all the values it would in a list context. It just returns one by one. Somehow, it has to tell you when it's done returning all the values. It does that by returning undef.

The first time you call glob, it returns the first filename that matches the file spec.

The second time you call glob, it returns undef since there are are no files that match the file spec passed to the first call to glob.

The quick fix is to do -f (File::DosGlob::glob qq{"$template_file"})[0] which puts the glob into list context.

No reason other than uninformed DWIMmery. :-)

Thanks, your suggestion works perfectly in my real code. Changing the first line here (and leaving the second alone) to:

    unless ( -f  ( File::DosGlob::glob qq{"$template_file"} )[0]    ) 
+{
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produces:

ftf2: 'file_a.txt'
ftf2a: '"file_a.txt"'
ftf2b: 'file_a.txt' is okay.

ftf2: 'file_b.txt'
ftf2a: '"file_b.txt"'
ftf2b: 'file_b.txt' is okay.


ftf3: 'file_b.txt'
ftf3a: '"file_b.txt"'
ftf2b: 'file_b.txt' is okay.

ftf3: 'file_a.txt'
ftf3a: '"file_a.txt"'
8251b: File check, cannot access 'file_a.txt', No such file or directo
+ry
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I guess my more important question is: why are you using glob()? Are these fileglobs or filenames? Why are you using glob() on something that's not a glob? Is it for some evil windows reason?

---

Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

First, my directories

> ls -1
abc.txt
def.txt
xyz.boo
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> perl -e '@a=qw(*.txt xyz.boo);foreach $f (@a) {print "$f->";$y=glob(
+$f);print $y,"\n";}'
*.txt->abc.txt
xyz.boo->def.txt
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> perl -e '@a=qw(*.txt xyz.boo);foreach $f (@a) {print "$f->";($y)=glo
+b($f);print $y,"\n";}'
*.txt->abc.txt
xyz.boo->xyz.boo
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I got bit once because I mistakenly believed that glob would always return files that only matched the inputs (with or without wildcards). In other words, the following is only true IF you use wildcards.

The first time you call glob, it returns the first filename that matches the file spec.

> ls -1
abc.txt
def.txt
xyz.boo
> perl -e '($y)=glob("*.txt");print $y,"\n";'
abc.txt
> perl -e '($y)=glob("boo.txt");print $y,"\n";'
boo.txt
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