Re: [9fans] mv on directory
> I know that. It's a copy, not move.
Looking at mv.c, I believe anything that's not a rename (ie move
within a directory) is a copy, then a hardremove. Mv(1) says the same
> I just can't see any reason why to mention anything about any bug. I
> didn't do that.
I wrote that because of this message:
from which I assumed you were extending the list you began there, and
because I support your bug-list idea generally, but *not* as a list
of places where, as I wrote before, "behavior deviates from the
similarly-named command in lunix." It's just boring.
> mkdir dirB
> dircp dirA dirB
> rm -r dirA[/color]
It seems like if you made that an rc(1) script and bound it over /bin/
mv, you'd have the desired behavior. No risk would be introduced to
the system, whether or not anyone (aside from the documentation, that
is) relies on mv(1) having the semantics of a wstat.
Given that even if mv(1) agreed to move a directory into another
directory, it would do so as a copy followed by a remove, I don't
understand what benefit there would be in changing mv. It seems like
you're essentially just calling dircp+rm -r by a different name,
which is so easy to do with name spaces.
All that said, it's not like I've never cursed a directory that
wouldn't mv for me in Plan 9 -- so if someone had an answer for Rob's
question: "What should mv do to a tree that resides on multiple file
servers?", it could be interesting to discuss. I don't think arguing
from rm -r is a good tact, though, because of the differing risk
levels between a failed delete and a failed move. One might afford
convenience in the former, and eschew it in the latter.
Re: [9fans] mv on directory
On Nov 1, 2008, at 9:30 AM, Josh Wood wrote:[color=blue]
> All that said, it's not like I've never cursed a directory that
> wouldn't mv for me in Plan 9 -- so if someone had an answer for
> Rob's question: "What should mv do to a tree that resides on
> multiple file servers?", it could be interesting to discuss. I don't
> think arguing from rm -r is a good tact, though, because of the
> differing risk levels between a failed delete and a failed move. One
> might afford convenience in the former, and eschew it in the latter.[/color]
That's a very good point. UNIX in general does guarantee certain
things about rename of the
subdirectories within the same FS, but the price they pay in the
kernel and elsewhere
(NFS being the prime example) seems just too high (the original
explanation given by a
friend of mine who wrote this was much more colorful, but I guess guys
like IBM & co. cleaned up
kernel comments quite a bit ;-)):
The behavior of mv(1) as defined by POSIX seems to build on top of the
guarantee, which, in case of Plan9 is not applicable. Thus it would be
an interesting thought
exercise to go over the POSIX text:
and see how much of the required subdirectory move semantics could be
preserved even though
we lack one of the basic building blocks that makes it behave like it
does on UNIX.