There is no more need to use a named pipe for cpu hashcat to use the PRINCE attack mode (Note: with oclHashcat you can simply pipe it, no named pipe needed at all) because version 0.49 of hashcat has a new attack mode: -a 6 = PRINCE which makes it more easy to use this attack mode (no more standalone princeprocessor needed).
See anouncement here:
https://hashcat.net/forum/thread-3952.html
See anouncement here:
https://hashcat.net/forum/thread-3952.html