RE: incompatible open modes

["Ata, John" <John.Ata@DigitalNet.com>]

Hi Andries,

If that's what's been decided... I presume for backwards compatability,
but it does seem rather odd though.  After all, it seems like O_RDONLY
is supposed to safeguard someone from accidently overwriting a file.
Otherwise why not automatically open everything read/write?  Going down
the same path, what's next: automatically write enabling a file which
has been openend for O_RDONLY the next time someone performs a write
operation on it? ;-)

Take care,
John

-----Original Message-----
From: Andries Brouwer [mailto:aebr@win.tue.nl] 
Sent: Thursday, July 31, 2003 1:36 PM
To: Zack Brown
Cc: Ata, John; Linux Kernel Mailing List
Subject: Re: incompatible open modes


> On Thu, Jul 31, 2003 at 12:09:14PM -0400, Ata, John wrote:

> >    the manpage on "open" states that if a file is opened
"O_RDONLY|O_TRUNC",
> >    the O_TRUNC is either ignored or an error is returned.  The 2.4
kernel
> >    appears to cheerfully truncate the file on open.  I wondered
which
> >    behavior is actually intended.
> >
> >    O_TRUNC
> >        If the file already exists and is a regular file  and  the
open
> >        mode  allows  writing  (i.e.,  is O_RDWR or O_WRONLY) it will
be
> >        truncated to length 0.  
> >        Otherwise the effect of O_TRUNC is unspecified.
> >        (On many Linux versions it will be ignored; on other versions
> >        it will return an error.)

This was just recently discussed, and it became clear that the
parenthetical
remark only led to confusion. It has been deleted. Instead

       The (undefined) effect of O_RDONLY | O_TRUNC various among
       implementations.  On  many  systems  the  file is actually
       truncated.

has been added.

Andries