File Permissions ?

[Paul Howarth]

akonstam at trinity.edu wrote:
> On Tue, Jan 10, 2006 at 06:47:25PM -0600, Jeff Vian wrote:
> 
>>On Tue, 2006-01-10 at 11:53 +1030, Tim wrote:
>>
>>>On Mon, 2006-01-09 at 14:39 -0600, Jeff Vian wrote:
>>>
>>>>Mode 004 is interpreted as "readable by everyone except owner or
>>>>group" (they are explicitly denied).
>>>>
>>>>To make it truly _world_ readable it needs to be mode 444.
>>>
>>>Are you sure?  I'd have thought that 404 would be sufficient, if the
>>>reasons offered were true.  A quick test proved it worked for me.
>>
>>It worked for you because you were the user (owner) and thus were
>>granted access by the 0404.  Someone who is in the group but is not the
>>owner would be denied.
>>
>>Try it with a test user and you will see what I mean.
>>
>>The permissions are parsed in sequence as <user -- group -- other> and
>>the _first_ one hit that allows/denies access is used. 
>>
> 
> Don't be too confident. Here is question . If a file has permissions
> 007 can the owner read it, change it , erase it?
> 
> The answer is no to the first two and yes to the last.

The ability to erase a file depends on the permissions of the directory 
containing it (and possibly its parents), not on the permissions of the 
file itself.

Paul.