It's probably more accurate to say it was intended to be the successor of UNIX. Plan 9 was developed by the same group that developed UNIX (Bell Labs) with man

It's probably more accurate to say it was intended to be the successor of UNIX. Plan 9 was developed by the same group that developed UNIX (Bell Labs) with many of the same prominent people credited with C and UNIX; Rob Pike, Ken Thompson, Dennis Ritchie. https://en.wikipedia.org/wiki/Plan_9_from_Bell_Labs https://en.wikipedia.org/wiki/Plan_9_from_Bell_Labs