Unable to locate source of empty value in an array in Perl

Question

I have stripped my code down to the bare basics in so many ways trying to find out why the very first value in my array is blank and I am stumped. I have an array of directories and files. If it's a directory or a file whose names contains a certain string (like "conf"), I'm not interested. If it's anything else, I write it to the screen and push it to an array object.

Then, I loop through the array and write each entry to the screen. That's all I'm trying to do. When I view what is printed to the screen in the first part, the information is as I'd expect. When I print out the entries in the array, the output always has an empty string or nothing in the first index of the array.

Here's my code:

sub scrubFiles { # Parse through interesting directories for interestingly named files
    my $wanted = sub {
            if (-d $_) {
                    print "Directory and will not be inserted into the files array: $_\n"
                    return;
            };
            if ($_ =~ /\.(?:yaml|bak|conf|cfg)\z/i) {
                    print "Not desirable and will not be inserted into the files array: $_\n";
                    return;
            };
            print ("Adding $_ to \@filelist\n");
            push @filelist, $File::Find::name;
    };
    find( {wanted => $wanted, no_chdir=>1}, @_ );  # WILL NOT work properly without no_chdir
    return @filelist;
}

&scrubFiles("/tmp/mydirectory/");
for (@filelist) { print "File name: $_|END\n"; }

I get the following output when pushing to the array. The "<...>" is output I just removed because its irrelevant. The "Adding" section contains exactly what I'd expect. There is nothing before the first "Adding" printed to the screen. When it gets to the "File name" part, it's exactly as I'd expect except the first entry in the array printed out to the screen is blank, as you can see here:

Adding /tmp/mydirectory/ifconfig.txt to @filelist
Adding /tmp/mydirectory/history_comp.txt to @filelist
Adding /tmp/mydirectory/myctl.txt to @filelist
Adding /tmp/mydirectory/ls-l.txt to @filelist
<...>
Adding /tmp/mydirectory/opt/comp/VERSION to @filelist
File name: |END
File name: /tmp/mydirectory/ifconfig.txt|END
File name: /tmp/mydirectory/history_comp.txt|END
File name: /tmp/mydirectory/myctl.txt|END
File name: /tmp/mydirectory/ls-l.txt|END
<...>
File name: /tmp/mydirectory/opt/comp/VERSION|END

I've tried using "ref()" to figure out what's actually in position 0 but it returns nothing for each entry in the array.

Any ideas how I could be getting this blank entry?

What happens when you compile your code with use strict; (and use warnings;)? The array @filelist referenced in scrubFiles appears to be a global variable of some sort; it isn't a my variable in the function, at any rate. I wonder if it is being pre-initialized with an empty entry? Have you tried doing for (@filelist) { print "Before $_\n"; } before you call scrubFiles? If you return the array from scrubFiles, why are you ignoring the returned value? — Jonathan Leffler
– Jonathan Leffler, Commented Jan 11, 2013 at 20:41
This was very helpful and led me to find the problem. I had "initialized" the array earlier in the program. Thanks! — harperville
– harperville, Commented Jan 11, 2013 at 20:55

ikegami · Accepted Answer · 2013-01-11 20:50:12Z

1

The code you had previously had properly scoped variables. You broke that. By going back to using global variables, we have to see every line in your program to know what's going on. That would be daft.

Start by going back to the code you were given to undo the two bugs you introduced. Declare @filelist in the sub, and actually use the list returned by the sub.

answered Jan 11, 2013 at 20:50

ikegami

391k17 gold badges291 silver badges555 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

harperville Over a year ago

@JohnathanLeffler's comment and your answer got me on the right track. Thank you so much. What a stupid mistake.

ysth Over a year ago

no, not a stupid mistake, one all too easy to make. and that's the whole point of being more conservative with variable scoping - limiting the too-easy mistakes you can make.

ikegami Over a year ago

@ysth, I think he meant he did my @filelist = ''; which he could just as easily have done in the sub, but your point stands nonetheless.

Collectives™ on Stack Overflow

Unable to locate source of empty value in an array in Perl

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related