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From: Will Senn <will.senn@gmail.com>
To: Clem Cole <clemc@ccc.com>
Cc: TUHS main list <tuhs@minnie.tuhs.org>
Subject: Re: [TUHS] moving directories in svr2
Date: Wed, 29 Dec 2021 09:44:32 -0600	[thread overview]
Message-ID: <d5b6f210-84e0-d9c7-3360-11e1dcbb6fcc@gmail.com> (raw)
In-Reply-To: <CAC20D2MozATvG1AK_QJe5ghz9NPL=vtW4dox7z0vShB-7nL+eQ@mail.gmail.com>

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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?
>
>

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  reply	other threads:[~2021-12-29 15:44 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-29 14:33 Will Senn
2021-12-29 15:02 ` arnold
2021-12-29 15:38   ` Will Senn
2021-12-29 15:44     ` Richard Salz
2021-12-29 16:17       ` Clem Cole
2021-12-29 16:58         ` Richard Salz
2021-12-30  5:14         ` Dan Stromberg
2021-12-30 16:22           ` Clem Cole
2021-12-30 18:02           ` John Cowan
2021-12-30 23:04             ` Richard Salz
2021-12-29 15:17 ` Clem Cole
2021-12-29 15:44   ` Will Senn [this message]
2021-12-29 16:10     ` Clem Cole
2021-12-29 16:33       ` Warner Losh
2021-12-29 16:01   ` Bakul Shah
2021-12-29 16:59 Bakul Shah
2021-12-29 17:04 ` Clem Cole
2021-12-29 17:14 ` arnold
2021-12-29 17:38   ` Clem Cole
2021-12-29 17:49     ` Brantley Coile
2021-12-29 18:27       ` ron minnich
2021-12-29 20:59         ` Rob Pike
2021-12-29 17:12 Douglas McIlroy
2021-12-29 19:13 Douglas McIlroy
2021-12-29 19:37 ` Dan Cross
2021-12-29 20:15   ` Dan Cross
2021-12-29 20:42     ` Richard Salz
2021-12-29 20:58       ` Dan Cross
2021-12-29 21:20         ` Clem Cole
2021-12-30  3:15       ` Bakul Shah
2021-12-29 19:33 Noel Chiappa
2021-12-30  3:40 ` Jay Logue via TUHS
2021-12-30  3:45 Noel Chiappa
2021-12-30  4:02 ` Bakul Shah
2021-12-30 16:40 ` Theodore Ts'o
2021-12-30 22:31   ` Dan Cross
2021-12-31  0:43     ` Bakul Shah
2021-12-31  1:00       ` Rob Pike
2021-12-31  1:45         ` Bakul Shah
2021-12-31  2:23           ` Adam Thornton
2021-12-31 18:56       ` Chet Ramey
2021-12-31  3:08     ` Theodore Ts'o
2021-12-31  3:23       ` Rob Pike
2021-12-31  5:16         ` Theodore Ts'o
2021-12-31  5:21           ` Dan Cross
2021-12-31  5:55           ` Rob Pike
2021-12-31 13:32             ` Michael Kjörling
2021-12-31 15:53               ` Adam Thornton
2021-12-31 16:13                 ` Arthur Krewat
2021-12-31 18:17                 ` Dan Cross
2021-12-31 18:23                   ` Larry McVoy
2021-12-31 18:37                     ` Dan Cross
2021-12-31 18:29                   ` Arthur Krewat
2022-01-01  0:09                   ` Theodore Ts'o
2022-01-03 13:35                     ` Dan Cross
2022-01-03 20:23                       ` Theodore Ts'o
2022-01-03 20:45                         ` Warner Losh
2022-01-03 21:15                         ` Dan Cross
2022-01-03 22:26                           ` Theodore Ts'o
2022-01-03 23:10                             ` Dan Cross
2022-01-04 15:45                             ` Chet Ramey
2022-01-09 19:28                             ` Larry McVoy
2022-01-03 23:21                           ` Doug McIntyre
2022-01-03 23:37                             ` Adam Thornton
2022-01-04 14:49                               ` Stuart Remphrey
2022-01-03 23:44                             ` Larry McVoy
2022-01-03 23:56                               ` Warner Losh
2022-01-04  2:28                               ` Theodore Ts'o
2022-01-04  2:42                                 ` Larry McVoy
2022-01-03 22:57                         ` Phil Budne
2021-12-31  5:12       ` Bakul Shah

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