Mac "Secure Empty Trash"

[Uncle Otto]

I have an iMac running Mountain Lion. As any Macoid knows, you can either delete something from the Trash folder the usual way, or you can use "Secure Empty Trash", which permanently removes files that cannot be recovered.

I like my Trash folder tidy, so I never have more than a dozen or so items in it. But if I use the Secure feature, it will sometimes say it's deleting nearly 5000 items, when I know I only had a few in there. I did a search on it but all I found was an old post at the Apple forum that said it has something to do with the external hard drive for back-ups.

It's not causing any problems, and it hasn't deleted anything I didn't want deleted. I'm just curious as to what's going on.

Any ideas from some fellow Mac users?

 

[elgarak]

I don't know the exact answer. So this is pure speculation.

I think that "Empty Trash" and "Secure Empty Trash" count files differently -- the former from the user POV, and the latter from a machine POV.

The file system on Mac OS X produces more files than you usually see, and keeps some of the hidden, and simplifies lots of them into bundles. For instance, it automatically includes a hidden "trash" folder in every folder you make (the Trash simply displays all those hidden "trash" folders combined). Then there's the "version" way of saving files, which I guess could be implemented by many different files bundled together into one document for us users. Plus, every folder counts as a separate file, but is not treated as such in the Finder. Lastly, an application file (.app) is nothing more as a folder that is locked down from normal access (you can still get into it with right-click>show package contents).

The way the Finder treats such hidden files has been often criticized by power users and developers. I, however, kinda like it since it is optimized for users who just want to get things done with the machine.

The "Secure Empty Trash" counts every file as it is actually there, including hidden files and bundles expanded into all the files that are in them.

The normal empty trash does not delete files; it simply overwrites the references to them. It's possible that when one deletes a folder, the normal empty trash simply deletes the reference to that folder, and NOT to all the files in the folder, as all references to those files originate at the folder, and are lost automatically when you trash the folder. It doesn't count the files in that folder, since all it has to do is cutting off the folder itself. With "Secure Empty Trash", the procedure needs to go in and follow up each file and overwrite the physical contents of each file.

I just did a quick test with a simple text file on my Desktop. Normal empty trash simply emptied the trash. There's no message since it was really just the one "file" (I should say document bundle) in there, just the "empty trash" sound. Doing a similar (same contents from my side, made with TextEdit in the exact same way) with "Secure Empty Trash" made a message pop up, and showed three files to delete.

ETA: Another test. Two folders, each with two files in them (for all intents and purposes identical to me as user).

Normal empty: No message, just the empty trash sound. Just like trashing a single file.

Secure Empty: Delay, message pops up, countdown starts with 5 files to delete.

 

[Uncle Otto]

Well that makes some sense. Especially with the bit about the folders. I knew all those files had to be connected to what I actually put in the Trash folder, I just didn't know how.