Just get the 4.1 man pages and it says: "Directories may only be moved
within the same parent directory."

On Wed, Dec 29, 2021 at 10:44 AM Will Senn <will.senn@gmail.com> wrote:

> On 12/29/21 9:17 AM, Clem Cole wrote:
>
> Not until the BSD rename system call,.
>
> Try it on V6 or V7 and you will get 'directory exists' as an error.
>
> Sure enough. I never really noticed. I guess cuz I was careful about
> creating directories in the first place.
>
> Think about the UNIX FS and the link system call. How is mv implemented?
> You link the file to the new directory and the unlink it from the old one.
>   But a directory file can not be in two directories at the same time as
> the .. link would fail.      When Joy created the rename system call it
> became possible.  Until System V picked it up (IIRC was SVR3), only system
> that supported the BSD world.
>
> Nice summary. I will add it to my systems programming investigations list.
>
> What I have forgotten is if the BSD mv command for 4.1 supported it.  If
> it did then it was not atomic -- it would have had to create the new
> directory, move the contents independently and then remove the old one.
>
> FWIW: when we did the first SMP UNIX at Masscomp we had supported the BSD
> FS and the 4.1c/4.2 system calls.   Joy's implementation of rename was a
> real mess.   Making it atomic, supporting an SMP and deal with all the
> recovery paths on an error took some work.  It's funny, the rename system
> call is a simple idea, but on a failure when partially thru it, makes
> unwinding the partial completion an interesting problem.
>
> It's impressive what early work was done and how few today really
> understand the challenges that were met and overcome to give us our cushy
> oses.
>
>
> Clem
>
> On Wed, Dec 29, 2021 at 9:34 AM Will Senn <will.senn@gmail.com> wrote:
>
>> I'm a little flummoxed in trying to move some directories around in svr2.
>> Shouldn't the following work?
>>
>>     mkdir a
>>     mkdir b
>>     mv a b
>>
>> I get the following error:
>>     mv: b exists
>>
>> I tried many of the possible variants including:
>>
>> mv a b/
>> mv: b/ exists
>> mv a b/a
>> mv: directory rename only
>> cd b
>> mv ../a .
>> mv: . exists
>> mv ../a ./
>> mv: ./ exists
>> mv ../a ./a
>> mv: directory rename only
>>
>>
>> If moving directories into existing directories wasn't allowed in those
>> days, 1) how were directories managed? and 2) when did moving directories
>> into directories become a thing?
>>
>>
>>
>