Re: curiosities with tempfile.active

[Chris Torek <chris.torek@gmail.com>]

On Sat, Aug 27, 2022 at 6:05 AM Jeff King <peff@peff.net> wrote:
> Yeah, I saw that. It's a bit vague, and if the call returns ENOSYS or
> EISDIR, that would be perfectly fine. It's the "what happens on the
> implementations that do support it..." part that I'm more worried about. :)

The history here is that pre-4.2BSD, Unix systems had no mkdir
system call. You used mknod() to make a truly empty directory and
the link() to create the "." and ".." entries within it, and all three of
these operations were restricted to the super-user.  There was no
rmdir either, so again, unlink() as the super-user was permitted to
do the job (with three calls to unlink the "." and ".." entries first and
then remove the directory).

Unlinking a directory when it still contains "." leaves the link count
at 1 and there's no GC, so it sits around occupying an inode.

If you have a mkdir() system call and don't need backwards
compatibility, you get to have these return EISDIR errors...

Chris