If your need is to total the size of an entire drive, then using

my @info = Win32::DriveInfo::DriveSpace( 'C' );
printf 'Total:%11d Used:%11d Free: %11d', 
       $info[5], $info[5]-$info[6], $info[6];

Total: 1076027392 Used: 1040338944 Free:    35688448
[download]

will return the same numbers as displayed on the properties tab for the specified drive in W.Explorer. This appears to be almost instantaneous.

However, if you need to find the size of a subdir tree, then the quickest way is to use Win32::OLE to access the Scripting.FileSystemObject (assuming you have this installed).

#! perl -sw
use strict;
use Win32::OLE;

my $fs = Win32::OLE->CreateObject('Scripting.FileSystemObject');

my $folder = $fs->GetFolder('e:/perl');
print 'e:\perl: ', $folder->size(), ' used', $/;

e:\perl: 52488590 used
[download]

This still needs to recurse the subdirs, but as it is done from within the OS in C, unsurprisingly it is considerably faster than you can do it yourself from Perl.

One further advantage of using the FileSystemObject is that subsequent calls to the size() function will reflect any changes to the folder or subtree without needing to re-calculate the numbers from scratch.

You could also look at the Win32::ChangeNotify API for a method of quickly discovering if any changes have occured in that part of the filesystem you are interested in. The changes that can be monotored include, file/directory names, sizes, attributes, security descriptors, and timestamps.

#!perl
use warnings;
use strict;
use Win32::OLE;

my $fs = Win32::OLE->CreateObject('Scripting.FileSystemObject');

my $dir = 'c:/s';
my $dir_obj = $fs->GetFolder($dir);
print $dir_obj->Size(), " bytes used\n";

__END__
Output:
38521553 bytes used
[download]

Great thanks, you are gold! :)

Ritter

Now, think about what you're asking Windows to do. Every time you change the allocation for a file, you want it to update that file's header, plus something in the directory the file resides in. Not only that, but you want this to work recursively so you need to update something in each directory on up to the root directory of the drive. That's an awful lot to do and a lot of disk I/O just to add a couple of blocks to a file.

When you ask for properties of a drive and it shows you the usage, that's for the drive as a whole. Windows does track that information. But if you were to click on 'Program Files', for example, you should notice that Windows goes and does exactly what you're trying to do with File::Find. The usage numbers don't come up immediately. You'll hear a lot of disk I/O going on and the numbers will gradually increment until it has finished scanning the heirarchy.

one point to differ on, Windows 2k xp etc cache this info so a second look is fast, you can do the same by using something like Cache::FileCache...

-Waswas