Ulrik S. Kofod wrote:
> I don?t understand why ".." isn?t working the same way for "ls" and "cd" when inside
> a symbolic link.
"cd" is shell builtin that attempts to be (too) smart. Since it is
shell builtin, it is able to remember where you think you are. There is
an extra code to implement this feautre. "pwd" builtin also behaves the
same. Try "pwd" followed by "/bin/pwd" to see the difference. Former
will return shell's best guess where you thing you are (and really this
is just a best guess). Later will return where you actually are.
While bash implements "ls" as shell builtin too, it does not attempt to
be "smart". When you do "ls .." it will simly read entry for ".." in
the actual file system structure which is going to point one directory
up from your actual position in file system.
Same goes for /bin/ls (which is a binary), or any other binary on the
system, that has no reliable way of knowing where you think you are
(unlike shell builtins that have the luxury of history). See the pwd
example described earlier. No, $PWD is not reliable way of knowing
where you think you are. $PWD is set by particular shell, and different
shells handle it differently (if they define it at all). Program that
would rely on it would produce different results for users of different
shells. Not a good thing.
Something like this would make your script work without creating links
for every possible file, buy you better make sure $PWD is set the way
you want it to be set by the interpretter that executes your script, and
that interpretter acutally inherits value of $PWD that was set by
calling shell:
$ mkdir -p a/b/c/d
$ ln -s ./a/b/c/d .
$ cd d
$ ls -l `dirname "$PWD"`
$ echo test > "`dirname "$PWD"`/test"
Or more complicated way that does not rely on existance and/or
correctness of $PWD:
$ mkdir -p a/b/c/d
$ ln -s ./a/b/c/d .
$ ln -s ../../../.. ./a/b/c/d/up
$ cd d
$ pwd
/tmp/d
$ /bin/pwd
/tmp/a/b/c/d
$ ls -l up/.
$ echo test > ./up/test
$ cd -
$ cat test
--
Aleksandar Milivojevic <amilivojevic@xxxxxx> Pollard Banknote Limited
Systems Administrator 1499 Buffalo Place
Tel: (204) 474-2323 ext 276 Winnipeg, MB R3T 1L7
