Inconsistent Symlinks

Set up directories as follows:

drwxr-xr-x   2 jtauber  staff   68 Mar 18 17:57 A
drwxr-xr-x   3 jtauber  staff  102 Mar 18 17:58 B
lrwxr-xr-x   1 jtauber  staff    3 Mar 18 17:58 C -> B/C

Now cd into B

jtmbp:TEST jtauber$ cd B

If you try to "execute" A from here, it tells you it's a directory

jtmbp:B jtauber$ ../A
-bash: ../A: is a directory

Now go back to the top directory

jtmbp:B jtauber$ cd ..

and cd into C (the symlinked directory)

jtmbp:TEST jtauber$ cd C

If you try to execute A from here, it can't find it via "../A" only "../../A"

jtmbp:C jtauber$ ../A
-bash: ../A: No such file or directory
jtmbp:C jtauber$ ../../A
-bash: ../../A: is a directory

so the attempt at execution is based on the actual absolute path, not the path based on following the symlink.

However,

jtmbp:C jtauber$ cd ../A
jtmbp:A jtauber$ 

So cd uses the path based on following the symlink but relative paths for execution do not.

I realise this is likely because cd is shell-based (and so knows the path that was followed to get to the current directory) whereas execution is a system call (which doesn't know the path that was followed to get to the current directory) but it's interesting nevertheless (and occasionally annoying).

This is on OS X but the behaviour is the same on Linux as far as I know.

Syndicated 2008-03-18 18:12:42 (Updated 2008-03-18 18:12:43) from James Tauber