fileDescriptor
The POSIX file descriptor associated with the receiver.
Declaration
var fileDescriptor: Int32 { get }Discussion
You can use this method to retrieve the file descriptor while it is open. If the file handle object owns the file descriptor, you must not close it yourself. However, you can use the closeFile() method to close the file descriptor programmatically. If you do call the closeFile() method, subsequent calls to this method raise an exception.