使用OS X中的IOKit框架的卷UUID

Question

I want to get / enumerate UUID of of volumes mounted on my OS X system. I know that I can use diskutil command to get it as below.

$ diskutil info / |grep "Volume UUID"
   Volume UUID:              039B9653-52AA-34F3-AF4A-854FA47C811A

However, I want to achieve it in a programmable way (maybe) using IOKit framework. If anyone can tell me how to do it, it will be very helpful.

Thanks a lot for your help in advance!

Answer 1

Thanks to @pmdj's answer, I could solve my issue with the following code snippet.

void printUUID()
{
    DADiskRef disk;
    CFDictionaryRef descDict;

    DASessionRef session = DASessionCreate(NULL);

    std::string mountPoint = "/";
    CFURLRef url = CFURLCreateFromFileSystemRepresentation(NULL, (const UInt8 *) mountPoint.c_str(), mountPoint.length(), TRUE);
    disk = DADiskCreateFromVolumePath(NULL, session, url);
    if (disk) {
        descDict = DADiskCopyDescription(disk);
        if (descDict) {
            CFTypeRef value = (CFTypeRef)CFDictionaryGetValue(descDict,
                                                              CFSTR("DAVolumeUUID"));
            CFStringRef strValue = CFStringCreateWithFormat(NULL, NULL,
                                                            CFSTR("%@"), value);
            printf("%s\n" ,CFStringGetCStringPtr(strValue, kCFStringEncodingMacRoman));
            CFRelease(strValue);
            CFRelease(descDict);
        }
        CFRelease(disk);
    }

    CFRelease(url);
    CFRelease(session);
}

Answer 2

Have you looked into the Disk Arbitration framework ? This is much better suited for volume enumeration, mount operations, etc., and allows you to query UUIDs among other properties., You can retrieve the IOService handle to the underlying IOKit objects as well, should you need them.

Note that both the HFS+ file system and the GPT partition on which it resides will have a UUID, and they will not match. diskutil generally talks about the HFS+ UUID.

Answer 3

There's a simpler way to get the UUID from a path that doesn't have to use the Disk Arbitration framework. The code below returns the volume UUID of the input full item path, using the NSURL's getResourceValue and the NSURLVolumeUUIDStringKey:

    NSURL* pathUrl = [NSURL fileURLWithPath:path];
    NSString* volumeUUID = nil;
    NSError* error = nil;
    BOOL success = [pathUrl getResourceValue:&volumeUUID forKey:NSURLVolumeUUIDStringKey error:&error];

Note that it does not enumerate the UUIDs of the mounted volumes, just gives you the volume UUID of the input path.