[ILUG] file permissions?

[paul at clubi.ie]

On Sat, 24 Jun 2006, Brian Foster wrote:

> fscked.  my guess is yer missing the appropriate eXecute permission 
> (which for dirs means search, i.e., scan thru a dir for a file, and

To be pedantic:

eXecute on a directory prevents /traversing/ that directory (ie 
access to any pathname below the directory is disallowed). One can 
still read the contents of a directory though, if one has 'Read' 
permission:

   $ ls -ld /tmp/testdir/
   drwxr-xr--  2 root root 80 Jun 25 03:34 /tmp/testdir/
   $ ls -l /tmp/testdir/
   total 0
   ?---------  ? ? ? ?           ? bar
   ?---------  ? ? ? ?           ? foo
   $ cat /tmp/testdir/bar
   cat: /tmp/testdir/bar: Permission denied

Note how read perms allows the directory to be read (ie get a list of 
files in that directory) but does not allow the files to be accessed 
in any way (e.g. stat(), open(), etc.).

And other way around, a directory without read permission disallows 
the directory from being read (so you can't list the files in the 
directory), but with execute set one can still access pathnames below 
the directory (if one already knows the pathname some other way, as 
you can't learn it from the directory):

   $ ls -ld /tmp/testdir/
   drwxr-x--x  2 root root 80 Jun 25 03:34 /tmp/testdir/
   $ ls -l /tmp/testdir/
   ls: /tmp/testdir/: Permission denied
   $ cat /tmp/testdir/bar
   baz
   $ ls -l /tmp/testdir/bar
   -rw-r--r--  1 root root 4 Jun 25 03:34 /tmp/testdir/bar

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
Fortune:
Maybe ain't ain't so correct, but I notice that lots of folks who ain't
using ain't ain't eatin' well.
 		-- Will Rogers