CocoaDev

How can I get the device ID (i.e. /dev/diskX) for a given path? I think you have to use the stat() function, but not 100% sure. Currently I’m just parsing the output of “/sbin/mount” which is ugly.

NSFileManager’s instance method fileSystemAttributesAtPath: might help. NSFileSystemNumber is the keyed attribute that gives you the file system number for the mounted file system that contains the path.

That method works, but since I’m trying to find the device ID of a volume, and the volume is mounted on /, NSFileSystemNumber always returns 0 (or whatever is /). But I figured out how to do it with straight C calls. You have to use getmntinfo() which gives you an array of all mounted file systems (/sbin/mount uses method I believe exactly). You’re also supposed to be able to use statfs() and pass it a file path, but I kept getting -1 from that function, not sure why. So I just created a function that loops through what getmntinfo() returns, and then created another function which parses the device ID (disk ID?) number from that:

#include <Cocoa/Cocoa.h> #include <sys/param.h> #include <sys/ucred.h> #include <sys/mount.h>

// see “man statfs” and “man getmntinfo”

NSString *mountedFileSystemForVolumePath(NSString *volume) { struct statfs *buf, *buf2; int i, count; const char *vol = [volume UTF8String];

count = getmntinfo(&buf, 0);
for (i=0; i<count; i++)
{
	if (strcmp(buf[i].f_mntonname, vol) == 0)
		return [NSString stringWithUTF8String:buf[i].f_mntfromname];
}
return nil; }

int deviceIDForVolumePath(NSString *volumePath) { NSString *mfs = mountedFileSystemForVolumePath(volumePath); if (mfs && [mfs hasPrefix:@”/dev/disk”] && [mfs length] > 9) { return mfs substringWithRange:[[NSMakeRange(9, 1)] intValue]; }

return -1;	 }

int main(int argc, char *argv[]) { if (argc == 2) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

	NSString *volume = [NSString stringWithUTF8String:argv[1]];
	int deviceID = deviceIDForVolumePath(volume);
	NSLog(@"deviceID: %d", deviceID);

	[pool release];
}

return 0; }