I personally have not seen any machine that will let you read the directory, a PC based CNC may be able to do something like this, but I doubt an older CNC would.
The closest thing I have seen for older machines etc, is almost a reverse procedure, a program like Cadem allows the CNC operator to remotely request a file from a distant, unattended computer and upload and download to it. This will work with almost every CNC that has a RS232 port.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.