29 Dec
2021
29 Dec
'21
2:33 p.m.
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?
29 Dec
29 Dec
3:02 p.m.
System V of that era didn't allow moving directories. You can copy them
recursively with find and cpio with the option that makes hard links
and then remove the old directory, or use a standard tar pipeline to
copy the directory tree.
BSD has always allowed moving directories; I *think* that descends
from Research Unix but I don't remember for sure.
HTH,
Arnold
Will Senn <will.senn(a)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?
3:38 p.m.
That's fascinating. I always wondered how oldtimers were so facile with
cpio and its ilk. If they had to use if for stuff like this, it's no
wonder they built some muscle memory on it.
Thanks,
Will
On 12/29/21 9:02 AM, arnold(a)skeeve.com wrote:
System V of that era didn't allow moving
directories. You can copy them
recursively with find and cpio with the option that makes hard links
and then remove the old directory, or use a standard tar pipeline to
copy the directory tree.
BSD has always allowed moving directories; I *think* that descends
from Research Unix but I don't remember for sure.
HTH,
Arnold
Will Senn <will.senn(a)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?
>
4:17 p.m.
Where and when did mvdir(1) appear? It's not in Research or BSD.
FWIW: in the old days, I just used tar cf - . | (cd some_place_else; tar
xvpf - ) preserving permissions. The hardlink scheme of cpio was the one
thing it could do that the original tar did not.
Clem
On Wed, Dec 29, 2021 at 10:46 AM Richard Salz <rich.salz(a)gmail.com> wrote:
Wasn't some of that handled by the mvdir
command?
30 Dec
30 Dec
5:14 a.m.
On Wed, Dec 29, 2021 at 8:18 AM Clem Cole <clemc(a)ccc.com> wrote:
Where and when did mvdir(1) appear? It's not in
Research or BSD.
FWIW: in the old days, I just used tar cf - . | (cd some_place_else; tar
xvpf - ) preserving permissions. The hardlink scheme of cpio was the
one thing it could do that the original tar did not.
I'm partial to:
(cd /source/dir && tar cf - .) | (cd /dest/dir && tar xfp -)
The &&'s make it so a typo is less likely to do something odd or even
damaging.
4:22 p.m.
sure - but old habits die hard (and Ken's man page for tar shows the form I
use. I programmed my fingers to his example in 1978 I suspect).
On Thu, Dec 30, 2021 at 12:14 AM Dan Stromberg <drsalists(a)gmail.com> wrote:
On Wed, Dec 29, 2021 at 8:18 AM Clem Cole <clemc(a)ccc.com> wrote:
Where and when did mvdir(1) appear? It's
not in Research or BSD.
FWIW: in the old days, I just used tar cf - . | (cd some_place_else;
tar xvpf - ) preserving permissions. The hardlink scheme of cpio was
the one thing it could do that the original tar did not.
I'm partial to:
(cd /source/dir && tar cf - .) | (cd /dest/dir && tar xfp -)
The &&'s make it so a typo is less likely to do something odd or even
damaging.
6:02 p.m.
On Thu, Dec 30, 2021 at 12:15 AM Dan Stromberg <drsalists(a)gmail.com> wrote:
FWIW: in the old days, I just used tar cf - . | (cd some_place_else; tar
In the new days, rsync -a dir1/ dir2 is the ticket (derived from "is
etiquette", if you can believe it). You need the terminating slash to
prevent dir1 from becoming a subdirectory of dir2; dir1/* would of course
not copy dotfiles. (I grew weary of typing "cp -r dir1/.[a-zA-Z]* dir2" to
copy dotfiles and dotdirectories left behind.) The -a flag ensures
permissions, symlinks, etc. are preserved.
If you rsync more than once, only the files in dir1 that have changed are
copied. You can also use user@host:path as either argument to make it
work over ssh, which is the common use case.
xvpf - )
preserving permissions.
11:04 p.m.
In the new days, rsync -a dir1/ dir2 is the ticket
...
If you rsync more than once, only the files in dir1 that have changed are
copied.
More then that. It uses a clever algorithm to send over only changes. It
was the basis of Tridgedell's PhD thesis.
https://www.samba.org/~tridge/phd_thesis.pdf
29 Dec
29 Dec
3:17 p.m.
Not until the BSD rename system call,.
Try it on V6 or V7 and you will get 'directory exists' as an error.
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.
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.
Clem
On Wed, Dec 29, 2021 at 9:34 AM Will Senn <will.senn(a)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?
3:44 p.m.
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(a)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?
4:10 p.m.
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(a)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(a)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?
4:33 p.m.
Kirk has said it took decades to get rename(2) right... it was by far the
hardest system call to get right, especially in the face of concurrency.
Warner
Warner
On Wed, Dec 29, 2021, 9:11 AM Clem Cole <clemc(a)ccc.com> wrote:
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(a)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(a)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?
>>
>>
>>
>
4:01 p.m.
On Dec 29, 2021, at 7:18 AM, Clem Cole <clemc(a)ccc.com> wrote:
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.
Don’t see why linking a dir in two places is a problem.
842
days inactive
843
days old
14 comments
8 participants
participants (8)
-
arnold＠skeeve.com -
Bakul Shah -
Clem Cole -
Dan Stromberg -
John Cowan -
Richard Salz -
Warner Losh -
Will Senn