The key in a file attribute dictionary whose value indicates the file's reference count.
The corresponding value is an NSNumber object containing an unsigned long.
The number specifies the number of hard links to a file.
Available in Mac OS X v10.0 and later.
Declaration Syntax Version Information- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)