If your Mac has multiple users set up—so your kids can log in under a different account and won’t be able to mess with your stuff, for example—you may have wondered just what you have access to outside of your own user folder and how you can share things back and forth. TMO’s Sandro Cuccia wrote an extensive article a while back about the Shared folder, which is one way to pass documents between users.
Of course, if you know the password for the other accounts on your machine, you can just log in and see all of each person’s files. If you don’t, though, navigating to Macintosh HD/Users/[someone else’s username] will look something like this:
All those red minus signs mean “hey, bub, stay outta here,” and double-clicking any one of those folders will tell you why.
What of that “Public” folder, though? It doesn’t have a red minus sign, so we can open it, right? Well, yes! “Public” is a special folder that you can use for file sharing on your Mac. Every user account has one, and it’s meant to allow you to read files that the owner wants to show you. So by default, anything that you put in your own Public folder can be read or copied (but not changed, moved, or deleted without administrator authorization) by any other user on your Mac. Similarly, you can read anything other users put in their own Public folders. One thing that’s confusing for some people, though, is that there’s an additional item that lives within each Public folder—the so-called Drop Box folder (not to be confused with the familiar Dropbox service, which’ll let you store and share files online).
Double-clicking someone else’s Drop Box folder only leads to more questions, however.
The secret here is that you can’t open another user’s Drop Box folder, but you can add items into it. Get it? So if a user on your Mac wants to share files with you, he can put them into his own Public folder. If you want to send files TO another user on your Mac instead, you can drag them into his Drop Box, but you won’t be able to see the items after you’ve done so.
It’s sort of like dropping a letter into a mailbox.
Examining the permissions for these folders may make the situation a bit more clear. Here’s what they are on the Public folder for another user on my system:
And here’s that user’s Drop Box folder:
Interesting, yes? The Public folder is read-only for everyone except the owner, and the Drop Box one is write-only. So it’s pretty easy to share stuff like pictures or other files with your kids on the family machine if you need to, as long as you understand how the permissions work.
One more piece of relevant info: Be wary of what you put in your Public folder if you have File Sharing turned on (within System Preferences> Sharing).
If that’s on, it’s possible for other people on your network to see and copy the contents of your Public folder, which may not be an issue at home but might be big-time trouble at your local coffee shop!
If you’re not using File Sharing, it’s best to just turn it off. Afterward, your machine will no longer advertise itself on the network, and your computing life will be a teensy bit more locked down. Or instead you could fill your Public folder with offensive files and wait for the inevitable reaction. That’s another way to go, I guess!