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From: ekrell@hector..UUCP (Eduardo Krell)
Newsgroups: comp.unix.wizards
Subject: Re: Symbolic Links
Message-ID: <2934@ulysses.homer.nj.att.com>
Date: Wed, 9-Sep-87 19:50:12 EDT
Article-I.D.: ulysses.2934
Posted: Wed Sep  9 19:50:12 1987
Date-Received: Sat, 12-Sep-87 00:36:15 EDT
References: <2931@ulysses.homer.nj.att.com> <1817@munnari.oz>
Sender: daemon@ulysses.homer.nj.att.com
Reply-To: ekrell@hector (Eduardo Krell)
Organization: AT&T Bell Labs, Murray Hill
Lines: 54

In article <1817@munnari.oz> mwp@munnari.UUCP writes:
   (me)
>> The original question was about removing a symbolic link, and how
>> could you tell the difference between removing the symbolic link and
>> the directory it points to.
>
>The point is that your implementation requires *more* sophistication
>form the average user than the BSD one. How many casual users know
>what lstat(2) does off the top of their heads?

What are you talking about? How can you tell if a file is a symbolic link
or not under BSD? That's right, lstat(). There's no other way!
The amount of code it would take (or the user-level command) to tell
the difference between a plain file/directory and a symbolic link is
under our implementation EXACTLY THE SAME AS IN BSD. Period.

>Explaining the BSD semantics requires only the model of a global jump
>to another part of the tree. Explaining situations which your semantics
>lead to requires detailed knowledge of symlinks and the way context can
>affect path names.

It only requires to know that /foo/bar/.. is the same as /foo (which is
the way I thought Unix worked).

>But with the idea of global jumps, this example is meaningless.

And I guess I can now dismiss your examples as meaningless with the idea
that /foo/bar/.. == /foo ?

>It seems to me that you are suggesting a change to the kernel because
>the semantics of "cd .." don't please you under the BSD system.

I made this clear a while ago: I use ksh on BSD, System V and all other
Unix systems we run. ksh treats "cd .." the way we propose to. I don't
need to "fix" the "cd .." problem, it's already taken care of by ksh.

>Your
>proposal certainly fixes this behaviour. There seem to be other ramifications
>of the scheme that far outweigh the proposed advantages, as has
>been pointed out by numerous examples.

I think the advantages clearly far outweigh these ramifications.
For every example you come up with, I can show you a counter-example which
is as simple as yours, in which BSD semantics breaks.

>I am not wholly against your ideas -- "cd .." really irks me on occasion.
>However, jumping in and changing the kernel may not be the best solution.

"cd .." can be "fixed" in the shell (see above). "ls .." can't, and I
believe "ls .." should be equivalent to "cd ..; ls"
    
    Eduardo Krell                   AT&T Bell Laboratories, Murray Hill

    {ihnp4,seismo,ucbvax}!ulysses!ekrell