> On Oct 21, 2019, at 19:58, Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:
> 
> Maybe that was a typo for 'mkdir as a system call'? (I recall having to do a
> fork() to execute 'mkdir', back when.) But 4.2 had mkdir().

I believe, it was 4.2 (or 4.1c) according to David Tilbrook's paper on rename. The site qef.com <http://qef.com/> seems to have disappeard, but the wayback machine has  copies[1]

	jaap

[1] as example, https://web.archive.org/web/20070228190911/http://www.qef.com/html/docs/rename.ps <https://web.archive.org/web/20070228190911/http://www.qef.com/html/docs/rename.ps>