I've never before bothered to make any of my code platform independent. Linux has been my predominant work platform for 8 years now. However I've recently started playing around on Windows, so have decided to explore creating code that is more platform independent.

I found the below code snippit to determine the parent directory of a script in one of my codebases:

use Cwd qw(abs_path);
use File::Basename qw(dirname);
 
my $dir_parent = abs_path(dirname(__FILE__) . '/../');
[download]

Now there is nothing inherently bad with this code. However, it hard-codes both the path separator and the .. parent directory alias. I therefore whipped out File::Spec , and come up with this monstrosity.

use File::Spec;

my $dir_parent = do {
    my ($vol, $dir, $file) = File::Spec->splitpath(
        File::Spec->rel2abs(__FILE__)
    );
    
    # Go up 1 directory
    my @dirs = File::Spec->splitdir($dir);
    pop @dirs while (@dirs > 1 && $dirs[-1] eq ''); # Clean up
    pop @dirs if @dirs > 1; # Go up 1 real directory.
    $dir = File::Spec->catdir(@dirs);
    
    File::Spec->catpath($vol, $dir);
};
[download]

Now this code is nice in a way as it only relies on File::Spec. But, god! It's soo long!

I've therefore decided to assume that '..' is a platform specific reference. That leaves me currently with the following code:

use File::Basename qw(dirname);
use File::Spec;

my $dir_parent = File::Spec->rel2abs(
    File::Spec->catdir(
        dirname(__FILE__),
        '..'
    )
);
[download]

Now, I've since adapted my code to no longer need this information. However, the above two questions still remain. How would y'all determine the parent directory of a script or module in a platform independent way?

Regards,
- Miller

PS

• I know that / can be used as a generic path separator on windows specifically. I do not believe this is true on other platforms though, and I'm curious for full platform independence.
• I looked at the source of both File::Find and File::Path to see if they used hardcoded references to '..', and File::Find does.