Subject: . and .. in the VFS (was: Re: Origin Of Filename Extension Dot Separator)

On 2026-08-24, Lawrence D?Oliveiro wrote:

On Mon, 24 Aug 2026 15:09:30 GMT, James Dow Allen wrote:

Lawrence D'Oliveiro <ldo@nz.invalid> posted:

Unix also copied the dot idea, but purely as a convention: the dot
was just another character that was valid in filenames, ...

Nitpick: The File-System does need to watch out for dot, but not for
extensions. It must detect the directory name ".." (and "."?).

Think of those as reserved entry names, nothing more. They have
nothing to do with the use of ?.? as any kind of ?separator?
character.

They are also completely unnecessary. They are a hangover from the
early days of the design of the Unix filesystem, and should have been discarded by now.

This is especially important if the user has been chroot'ed into a
sandbox or play-pen.

They require special treatment from the kernel anyway, which is why
putting explicit entries for them into every directory is such a waste
of space and time.

As opposed to even more special treatment for some other implementation
of the same?

How would you implement "current directory" and "parent directory"?

--
Nuno Silva

--- PyGate Linux v1.5.19
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 25/08/2026 7:20 AM, Nuno Silva wrote:

On 2026-08-24, Lawrence D?Oliveiro wrote:

On Mon, 24 Aug 2026 15:09:30 GMT, James Dow Allen wrote:

Lawrence D'Oliveiro <ldo@nz.invalid> posted:

Unix also copied the dot idea, but purely as a convention: the dot
was just another character that was valid in filenames, ...

Nitpick: The File-System does need to watch out for dot, but not for
extensions. It must detect the directory name ".." (and "."?).

Think of those as reserved entry names, nothing more. They have
nothing to do with the use of ?.? as any kind of ?separator?
character.

They are also completely unnecessary. They are a hangover from the
early days of the design of the Unix filesystem, and should have been
discarded by now.

This is especially important if the user has been chroot'ed into a
sandbox or play-pen.

They require special treatment from the kernel anyway, which is why
putting explicit entries for them into every directory is such a waste
of space and time.

As opposed to even more special treatment for some other implementation
of the same?

How would you implement "current directory" and "parent directory"?

I believe what our esteemed Python influencer, Lawrence D'Oliveiro meant
to say, that we should all be using the OpenVMS syntax, even in Posix
operating systems, and that is

SET /DEFAULT [-]

for the parent directory, and possibly

SET /DEFAULT []

for the actual current directory. I admit my recollection of the
OpenVMS D.C.L. command set has been fading from my memory, because I
haven't used it much since Deathrow got annihilated; for that reference,
I hope alt.folklore.computers is up to the task of searching their
memory, but it was a famous OpenVMS cluster ca. twenty years ago.


So I have added comp.os.vms to the discussion, and they are free to
correct my D.C.L.
--
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--- PyGate Linux v1.5.19
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> writes:

I believe what our esteemed Python influencer, Lawrence D'Oliveiro meant
to say, that we should all be using the OpenVMS syntax, even in Posix operating systems, and that is

SET /DEFAULT [-]

for the parent directory, and possibly

SET /DEFAULT []

for the actual current directory.

Close - leave off the "/". There's a little "cd" tool you can use
because "set default" is clunky. Before someone points it out, yes, you
can shorten "default" to "set def".

https://vmssoftware.com/software/freeware/CD.zip

$ set default [.CKU416-BETA12]
$ set default []
$ set default [-]
$ show default
DUA1:[JAYJWA]
$ cd [.netscape]
$ show default
DUA1:[JAYJWA.NETSCAPE]
$ cd ~
$ show default
DUA1:[JAYJWA]
$

TOPS-20 works in a similar way, but with "connect" (I set a logical for
"cd") and "<" ">". Or, use the "cz" tool that's floating around the T20 software sites.

@info logical cd
Job-wide:

cd: => CONNECT
@cz dsk1:<programming>
[From: TOPS20:<JAYJWA>]
[To: DSK1:<PROGRAMMING>]
@cd <.file>
@info dirECTORY (DIRECTORY NAME)
Name DSK1:<PROGRAMMING.FILE>
Working disk storage page limit 350
Permanent disk storage page limit 300
DECNET-ACCESS
FILES-ONLY
Number of directory 23
Account default for LOGIN - none set
Protection of directory 775252
Generations to keep 3
TOPS10 project-programmer number - none set
@cd <..>
@info dirECTORY (DIRECTORY NAME)
Name DSK1:<PROGRAMMING>
...

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--- PyGate Linux v1.5.19
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On Thu, 03 Sep 2026 11:29:15 -0400, jayjwa wrote:

TOPS-20 works in a similar way, but with "connect" (I set a logical
for "cd") and "<" ">". Or, use the "cz" tool that's floating around
the T20 software sites.

If there is one pathname syntax convention that I would say was
slightly more rational than that in Unix, it would be the Multics one.

--- PyGate Linux v1.5.19
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 9/3/2026 9:20 PM, Johann 'Myrkraverk' Oskarsson wrote:

I believe what our esteemed Python influencer, Lawrence D'Oliveiro meant
to say, that we should all be using the OpenVMS syntax, even in Posix operating systems, and that is

SET /DEFAULT [-]

dBase has the SET DEFAULT command as well.

dbase set default - Google Search <https://www.google.com/search?q=dbase+set+default>

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* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)