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From: Keith Thompson <kst@cts.com>
Subject: Re: if file exist
Date: 06 Oct 2002 13:35:21 -0700
Date: 2002-10-06T13:35:21-07:00	[thread overview]
Message-ID: <yecadlrcnli.fsf@king.cts.com> (raw)
In-Reply-To: wccelb5nfz7.fsf@shell01.TheWorld.com

Robert A Duff <bobduff@shell01.TheWorld.com> writes:
[...]
> I'm not sure what the second command is attempting to do, but I'm pretty
> sure that on Unix systems, if you have no access to directory "dir"
> (i.e., rwx bits all zero), then you can't find out whether a given file
> name exists in dir.  E.g., "ls dir/exists" and "ls dir/not-exists" will
> both produce the same error message, even though exists exists and
> not-exists does not.  Attempting to run a directory as a command will
> cause an error, too, so I don't see how the second command causes a
> security flaw.  Please explain the 'ls `dirname filename`'.

I think you missed the backticks and/or the fact that "dirname" is a
Unix command that prints a given filename with the trailing component
removed.  (It's a litle confusing; "dirname" is a literal command
name, and "filename" substitutes for the actual name of some file.)

So the command

    ls `dirname /etc/motd`

expands (well, contracts actually) to

    ls /etc

-- 
Keith Thompson (The_Other_Keith) kst@cts.com  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center           <*>  <http://www.sdsc.edu/~kst>
Schroedinger does Shakespeare: "To be *and* not to be"



  reply	other threads:[~2002-10-06 20:35 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <mailman.1032687678.1150.comp.lang.ada@ada.eu.org>
2002-09-22  9:58 ` if file exist Preben Randhol
2002-09-22 19:25   ` Keith Thompson
2002-09-22 11:26 ` Dale Stanbrough
2002-09-22 14:45   ` Simon Wright
2002-09-22 17:24     ` Frank J. Lhota
2002-09-22 19:24     ` Keith Thompson
2002-09-22 22:20     ` Dale Stanbrough
2002-09-23  5:14       ` Simon Wright
2002-09-23 12:38         ` Larry Kilgallen
2002-09-26  0:39           ` Nick Roberts
2002-09-26 16:48             ` Warren W. Gay VE3WWG
2002-09-26 22:14               ` Robert A Duff
2002-09-27 10:47                 ` steve_H
2002-09-27 14:01                   ` Robert A Duff
2002-09-27 18:43                   ` Randy Brukardt
2002-09-28  1:17                     ` Keith Thompson
2002-09-28 13:04                       ` Marin David Condic
2002-09-29  4:50                         ` Keith Thompson
2002-09-29  5:13                           ` Christopher Browne
2002-09-27 21:59                   ` Mark Biggar
2002-09-27 23:09                     ` Larry Kilgallen
2002-10-04 20:56                     ` Stefan Skoglund
2002-10-05 13:59                       ` Robert A Duff
2002-10-06 20:35                         ` Keith Thompson [this message]
2002-10-07  0:34                       ` Robert A Duff
2002-10-07  5:42                     ` David Thompson
2002-10-13 17:05                       ` Larry Kilgallen
2002-10-21  2:17                         ` David Thompson
2002-09-22 11:55 ` Per Sandbergs
2002-09-22 22:29 ` SteveD
2002-09-23  1:53   ` if_file_exist : it's working thankyou all! Dominic D'Apice
2002-09-23  5:25     ` Simon Wright
2002-09-23 23:59       ` Dominic D'Apice
2002-09-25 19:13         ` Simon Wright
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