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Date: Sun, 15 Sep 2002 12:07:49 +0100
From: Raphael <raphael AT oninet DOT pt>
To: cygwin AT cygwin DOT com
Subject: Re: Crontab problems
Message-ID: <20020915110749.GA1804@TOOS>
Mail-Followup-To: cygwin AT cygwin DOT com
References: <20020914200118 DOT GA1032 AT TOOS> <Pine DOT GSO DOT 4 DOT 44 DOT 0209141950270 DOT 21486-100000 AT slinky DOT cs DOT nyu DOT edu>
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On Sat, Sep 14, 2002 at 07:55:36PM -0400, Igor Pechtchanski wrote:
> On Sat, 14 Sep 2002, Raphael wrote:
>=20
> > On Sat, Sep 14, 2002 at 01:00:20PM -0400, Igor Pechtchanski wrote:
> > > On Thu, 12 Sep 2002, Raphael wrote:
> > >
> > > > On Wed, Sep 11, 2002 at 05:53:24PM -0400, Igor Pechtchanski wrote:
> > > > > On Wed, 11 Sep 2002, Nicholas Wourms wrote:
> > > > >
> > > > > > --- Raphael <raphael AT oninet DOT pt> wrote:
> > > > > > > Hi guys/girls~,
> > > > > > >
> > > > > > > I'm having a bit of a problem with my windows based editor. U=
sing
> > > > > > > it with
> > > > > > > Pine or Mutt is not problem. Using it with Crontab -e gives a
> > > > > > > sharing
> > > > > > > violation error when I want to save the new file.
> > > > > > >
> > > > > > > Is this a crontab problem?
> > > > > >
> > > > > > Use vi.exe
> > > > >
> > > > > Most windows editors adopt a remove-and-recreate (or rename-and-r=
ecreate)
> > > > > policy.  This basically means that they will try to remove or ren=
ame the
> > > > > crontab-created file (which will fail, silently), and then create=
 that
> > > > > file over (which will fail since crontab has it open).  This is w=
here your
> > > > > sharing violation comes from.
> > > >
> > > > Ok, I can understand that explenation.
> > > >
> > > > > I've verified this with notepad and
> > > > > editpad, but I'm sure most of the others will behave similarly.  =
Thus,
> > > > > looks like using a cygwin-based editor is your only option, unles=
s you can
> > > > > find a windows one that writes the files in-place.  If this creat=
es one
> > > > > more convert for the vi camp, all the better. ;-)
> > > >
> > > > Don't think so, why should Cron not be able to act like Pine or Mut=
t. I
> > > > guess the latter start opening the file in shared mode?
> > >
> > > I don't know about mutt, but pine, IIRC, does not keep the file open =
while
> > > it's being edited by an external editor.  It re-opens the file afterw=
ards,
> > > which is why it doesn't care whether it's the same file, or a newly
> > > created one.
> >
> > Hi Igor,
> > But do you have any idea why Cron shouldn't be able to act the same?
>=20
> Quoting straight from the crontab-3.0.1-7 source (crontab.c:418):
>=20
>         /* we still have the file open.  editors will generally rewrite t=
he
>          * original file rather than renaming/unlinking it and starting a
>          * new one; even backup files are supposed to be made by copying
>          * rather than by renaming.  if some editor does not support this,
>          * then don't use it.  the security problems are more severe if we
>          * close and reopen the file around the edit.
>          */
>=20
> Hope this answers your question. =20

Hmmm, it answers the question, but raises others. I cannot see the security=
=20
issue for Cygwin as I now work arround by editing /var/cron/tabs/<currentus=
er>
directly and restarting the service afterwards.

> By the way, the patch to close the file
> and re-open it is trivial, and is left as an exercise for the reader.

Great but without any C knowledge I wouldn't even know where to start. I'm=
=20
wondering, if Corinne is reading this, if the patch might not be standarize=
d=20
for Cygwin considering the interchangability between Cygwin and Windows.
Ofcourse only if there is really no security issue.

> Boy, I get to quote the source a lot these days...  Not that I'm
> complaining or anything... :-D

I'm sure everyone is very greatfull for you sharing this information. It's
considarably more informative than a blunt =B4Use vi.exe=B4 some people try
to kill a thread with. Thank you very much.

Kind Regards

Raphael.
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