How to get default volume on Mac OS X 64-bit?

Answer 1

Well. I don't really know what "default volume" is. All I know is that Carbon manual (File Manager) says:

ioVRefNum A volume reference number, 0 for the default volume, or a drive number.

Well, I seem to find the answer for my question.

FSVolumeInfoParam vol_info = { 0 };
vol_info.ioVRefNum = kFSInvalidVolumeRefNum; // will obtain it
vol_info.volumeIndex = 1; // XXX: is it the default volume as well?
vol_info.whichInfo = kFSVolInfoNone; // don't pass volume info
err = PBGetVolumeInfoSync(&vol_info);

The only thing I'm not sure of is if the 1st volume is the default one...

P.S. I guess the problem is that I don't quite understand what "default volume" really is ;-)

Answer 2

In the File Manager docs, you'll notice a function group titled “Manipulating the Default Volume”. All of those functions are deprecated.

If you search Google for the functions therein, particularly HSetVol, you'll find this mailing list post by Eric Schlegel, which says HSetVol had the effect of setting the current working directory (expressed as a volume/directory pair) on Mac OS. He also says that it doesn't work on Mac OS X: It should work on File Manager functions, but does not set the working directory used for resolving relative paths in other APIs (e.g., open and fopen) like it did on Mac OS.

Moreover, those functions are not available in 64-bit Mac OS X. So the answer is: You don't, because there is no default volume.

The old meaning of it was analogous to the current working directory, so you can do the same thing by getting the CWD and resolving that path to an FSRef. However, for a Mac OS X application (particularly one that doesn't set the CWD by any means, as most don't), this is not terribly useful: The default CWD for an application is /, the root directory of the boot volume. On the other hand, if you run your executable directly or under Xcode's Debugger, its CWD will not be /, which means it could be some other volume—most probably, the one with your Home folder on it.

You should refer to the boot volume (or whatever volume you're interested in) specifically, not attempt to get or simulate getting the default (current working) directory.

For the boot volume, you might try kOnSystemDisk, which is one of the constants in the Folder Manager. If that doesn't work, use Folder Manager's FSFindFolder function to retrieve the System folder, then use File Manager's FSGetVolumeInfo function to get what volume it's on.