I used to port Unix for a living (V6 thru SysVr3) I know it was in Vr2, and I have a man page that says "(last mod. 1/15/87)" which would likely make it SysVr1 or earlier
I used to port Unix for a living (V6 thru SysVr3) I know it was in Vr2, and I have a man page that says "(last mod. 1/15/87)" which would likely make it SysVr1 or earlier
(My guess is that it dates from the introduction of fsck which from memory was V7 or later)
My guess is that it was undocumented until Release 3 or 4, so the book authors simply never found out about it. Andrew Tanenbaum knew about it at the same time as the first Hunter and Fielding book, but likely this was word-of-mouth stuff.
* https://groups.google.com/g/comp.unix.wizards/c/bbCYhh7_r-8/...
Enjoy the obvious question asked about all this, way back in November 1981:
* https://groups.google.com/g/fa.unix-wizards/c/h5mFGIV91Io/m/...
That's the Dave Yost, still at RAND at the time, who went on to make the GRAND Editor.
* https://news.ycombinator.com/item?id=43734536