How to make a minecraft source file to hold files for both a windows and a mac version, both held on the same USB?

Question

I recently made a "minecraft usb" that allows me to play minecraft on both a windows, and a mac machine (my main machine.) The root directory has two folders, "MC_MAC" and "MC_WIN". Everything works great, but I'm looking for a way to make the two installations use the same "saves" file, so that I don't have to keep copying and recopying worlds from the Mac "saves" to the "windows" saves.

I thought of using the "Alias" function on mac, but that probably wouldn't translate well onto a windows machine.

Thoughts?

(Bonus points for getting the one "source" file to sync with the saves file on my mac when I plug in the usb...)

[Edit]

So far, I've got answers about how to run minecraft completely off a USB. This isn't my problem, I've gotten the game to work fine on both mac and windows, running completely off my 16GB Flash-drive, and leaving no trace (so far as I can tell) on the host machine, be it windows or mac.

Seeing as the MC for mac is a .app and MC for windows is a .exe, I can't use one install on both computers. And seeing as I have two installs, with each one generating it's own set of files, I have two save folders.

What I need is some way to make both installs read from and write to just one save folder.

Answer 1

I understand that you have modified Minecraft so that it writes onto the USB drive, but not in the same place for each version. All you need is a symlink to make the Mac side do what you want.

First, delete the Mac side's saves, then in a shell, run the following (based on your comment mentioning the path for Mac; adjust the path to the Windows side as needed):

cd '/Volumes/myusb/Library/Application Support/Minecraft'
ln -s '../../../whatever-the-path-is-to-the-windows-side/saves' ./saves

If I haven't got the Mac-side path right, then make sure the count of ..s is adjusted to match. To test your symlink, run ls saves and you should see your list of worlds.

Most applications, including Minecraft, will follow a symlink as if it is not there, so this should do the trick. (Note that when viewed by the Finder, a symlink appears identical to an alias, but an alias will not function as needed here. An alias is more like a Windows shortcut — it is not automatically traversed by file system calls.)