Re: AUTO_CD (-J) with CDPATH problems

[Peter Stephenson <pws@xxxxxx>]

heiko_elger@xxxxxxxxxx wrote:
> I have problems using the "AUTO_CD" option with zsh.
> 
> 0:~/jobs> prom          --> is expanded to cd ~/prom
> 0:~/prom> 
> 
> But over the day the same command produces the following error:
> 
> 0:~/jobs> prom
> zsh: the file access permission do not allow the specified action.: prom
> 
> But my access prmissions are still the same
> 0:~> ls -ld prom
> drwxr-xr-x    9 ente59   staff 3584 Sep 28 7:29 prom

The problem arises if the command name `prom' is hashed, i.e. in zsh's
internal tables of where commands are to be found.  For some reason,
this will happen even to subdirectories of a directory of $path ---
the whole of a directory in $path, not just commands, are added to the
command hash table.  So if ~ is in $path, prom is hashed as a command;
then instead of assuming a cd, the shell tries to execute it, but
can't, because it isn't a command.

(The reason it doesn't happen straight away is simply that the
directory doesn't get hashed until the shell needs to look for a
command there.)

I know the same feature has been causing trouble with completion for
some time, but this seems to be the last straw.  I presume hashdir()
does not check individual files for speed.  I could instead write a
function isreallycommand() to test permissions and add it in strategic
places in execcmd() and the completion code.  However, doing it in the
completion code is potentially very slow as well --- in the worse case
it may have to stat() every single hashed command.  I could alleviate
this by getting isreallycommand() to throw out the duff entries and
add a flag for the others (the command may have been moved, of course,
but that's what rehash is for).  However, did anybody ever check how
much slower it was to stat() the entire directory when adding it to
the command hash table?

I can make a minimal patch just for AUTO_CD when the single
stat()/access() is cheap, of course (in fact I've got one), but I'd
prefer to attack the root cause if possible.

-- 
Peter Stephenson <pws@xxxxxx>       Tel: +39 50 844536
WWW:  http://www.ifh.de/~pws/
Gruppo Teorico, Dipartimento di Fisica
Piazza Torricelli 2, 56100 Pisa, Italy