访问单个文件的元数据

Question

Is there a way to programmatically access metadata of a single file on MacOS?

I know Apple provides NSMetadataQuery , but it seems it only allows to search in particular folders for files matching some parameters. Actually I'd prefer not to search for all files matching but check if a particular file matches.

Is there a way or the only solution is to analyze the results of the query and see if my file is among them?

Answer 1

You can get the metadata the same way the command mdls gets its data. Search for MDItemCreate in the documentation. (you find : Core Library --> Data Management --> File Management --> MDItem Reference )
I hope the following method to create the metadata dictionary will give you what you need:

- (NSDictionary *) metaDataDictionaryForFileAt:(NSString *)fileName
{
    MDItemRef item = MDItemCreate( kCFAllocatorDefault, (CFStringRef)fileName );
    if( item==nil ) return nil;

    CFArrayRef list = MDItemCopyAttributeNames( item );
    NSDictionary *resDict = (NSDictionary *)MDItemCopyAttributes( item, list );
    CFRelease( list );
    CFRelease( item );
    return [resDict autorelease];
}

Remark : The value of kMDItemContentType , kMDItemContentTypeTree , and kMDItemKind are determined by the suffix of the filename not by the content of the file!

Answer 2

I don't think there's an API for this (which is odd, you should file a bug). If you don't want to run a query then your only other option would be to use NSTask to spawn an instance of the mdls command and then parse the results.