* RE: unlink() problem
@ 2001-08-08 12:49 John Wiersba
2001-08-08 12:58 ` Larry Hall (RFK Partners, Inc)
0 siblings, 1 reply; 6+ messages in thread
From: John Wiersba @ 2001-08-08 12:49 UTC (permalink / raw)
To: 'Larry Hall (RFK Partners, Inc)', 'cygwin'
Thanks for your reply, Larry. Unfortunately, this is a bad bug since the
simple perl script below removes the original file (whoops!) since it
assumes that if you have permission to unlink the original file, then you
have permission to create a new file of the same name (I believe this is
always true on unix). The net result is that you lose your data.
I can't think of anyway around it except to know that you can't do inplace
editing on cygwin.
-- John Wiersba
> -----Original Message-----
> From: Larry Hall (RFK Partners, Inc) [ mailto:lhall@rfk.com ]
> Sent: Tuesday, July 31, 2001 6:59 PM
> To: John Wiersba; 'cygwin'
> Subject: Re: unlink() problem
>
>
> At 06:22 PM 7/31/2001, John Wiersba wrote:
> >I'm having a problem with unlink(). I've scanned the FAQ
> and searched some
> >in the newsgroup archives for information about the
> following problem. I
> >did find a post (see
> > http://sources.redhat.com/ml/cygwin/2001-05/msg01095.html )
> but no apparent
> >resolution.
> >
> >$ touch asdf
> >$ perl -i -pe 1 asdf
> >Can't do inplace edit on asdf: Permission denied.
> >
> >What perl is doing is equivalent to:
> >
> >$ perl -e '
> > open A, "< asdf" or die "one $!"; # open asdf for read
> > unlink "asdf";
> > open B, "> asdf" or die "two $!"; # open asdf for write
> > while (<A>) { print B } # copy from A to B
> >'
> >two Permission denied at -e line 4.
> >
> >The problem: after the unlink(), I can't open the same
> filename for write
> >as I can on unix. If I pause the program after unlinking
> asdf, it is still
> >there and can be seen by ls, but can't be read by ls -l.
> >
> >Is there a workaround for this behavior? Is it considered a
> bug or is it
> >just a quirk of the cygwin implementation of trying to implement unix
> >filesystem semantics on top of windows?
>
>
> The latter. This has been quite a day for this issue! This is the
> third time it came up. Perhaps this qualifies as an FAQ now! ;-)
>
> See my previous posts about this subject from earlier in the day:
>
> http://www.cygwin.com/ml/cygwin/2001-07/msg01797.html
> http://www.cygwin.com/ml/cygwin/2001-07/msg01774.html
>
> There's also a related FAQ, although the message it mentions doesn't
> seem to pop up anymore, which gives insight into the underlying
> implementation. See:
>
> http://www.cygwin.com/faq/faq_4.html#SEC57
>
> Of course, the code is the "last word" on this subject in terms of the
> actual implementation.
>
>
>
>
>
>
>
> Larry Hall lhall@rfk.com
> RFK Partners, Inc. http://www.rfk.com
> 118 Washington Street (508) 893-9779 - RFK Office
> Holliston, MA 01746 (508) 893-9889 - FAX
>
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^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: unlink() problem
2001-08-08 12:49 unlink() problem John Wiersba
@ 2001-08-08 12:58 ` Larry Hall (RFK Partners, Inc)
0 siblings, 0 replies; 6+ messages in thread
From: Larry Hall (RFK Partners, Inc) @ 2001-08-08 12:58 UTC (permalink / raw)
To: John Wiersba, 'cygwin'
At 03:47 PM 8/8/2001, John Wiersba wrote:
>Thanks for your reply, Larry. Unfortunately, this is a bad bug since the
>simple perl script below removes the original file (whoops!) since it
>assumes that if you have permission to unlink the original file, then you
>have permission to create a new file of the same name (I believe this is
>always true on unix). The net result is that you lose your data.
>
>I can't think of anyway around it except to know that you can't do inplace
>editing on cygwin.
Right. I suppose if one could queue up the file creation as well,
this might help. Still it ain't UNIX semantics by a long shot!
> > -----Original Message-----
> > From: Larry Hall (RFK Partners, Inc) [ mailto:lhall@rfk.com ]
> > Sent: Tuesday, July 31, 2001 6:59 PM
> > To: John Wiersba; 'cygwin'
> > Subject: Re: unlink() problem
> >
> >
> > At 06:22 PM 7/31/2001, John Wiersba wrote:
> > >I'm having a problem with unlink(). I've scanned the FAQ
> > and searched some
> > >in the newsgroup archives for information about the
> > following problem. I
> > >did find a post (see
> > > http://sources.redhat.com/ml/cygwin/2001-05/msg01095.html )
> > but no apparent
> > >resolution.
> > >
> > >$ touch asdf
> > >$ perl -i -pe 1 asdf
> > >Can't do inplace edit on asdf: Permission denied.
> > >
> > >What perl is doing is equivalent to:
> > >
> > >$ perl -e '
> > > open A, "< asdf" or die "one $!"; # open asdf for read
> > > unlink "asdf";
> > > open B, "> asdf" or die "two $!"; # open asdf for write
> > > while (<A>) { print B } # copy from A to B
> > >'
> > >two Permission denied at -e line 4.
> > >
> > >The problem: after the unlink(), I can't open the same
> > filename for write
> > >as I can on unix. If I pause the program after unlinking
> > asdf, it is still
> > >there and can be seen by ls, but can't be read by ls -l.
> > >
> > >Is there a workaround for this behavior? Is it considered a
> > bug or is it
> > >just a quirk of the cygwin implementation of trying to implement unix
> > >filesystem semantics on top of windows?
> >
> >
> > The latter. This has been quite a day for this issue! This is the
> > third time it came up. Perhaps this qualifies as an FAQ now! ;-)
> >
> > See my previous posts about this subject from earlier in the day:
> >
> > http://www.cygwin.com/ml/cygwin/2001-07/msg01797.html
> > http://www.cygwin.com/ml/cygwin/2001-07/msg01774.html
> >
> > There's also a related FAQ, although the message it mentions doesn't
> > seem to pop up anymore, which gives insight into the underlying
> > implementation. See:
> >
> > http://www.cygwin.com/faq/faq_4.html#SEC57
> >
> > Of course, the code is the "last word" on this subject in terms of the
> > actual implementation.
> >
> >
> >
> >
> >
> >
> >
> > Larry Hall lhall@rfk.com
> > RFK Partners, Inc. http://www.rfk.com
> > 118 Washington Street (508) 893-9779 - RFK Office
> > Holliston, MA 01746 (508) 893-9889 - FAX
> >
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^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: unlink() problem
@ 2001-08-09 9:31 Robinow, David
0 siblings, 0 replies; 6+ messages in thread
From: Robinow, David @ 2001-08-09 9:31 UTC (permalink / raw)
To: 'cygwin'
> -----Original Message-----
> From: Robinow, David [ mailto:drobinow@dayton.adroit.com ]
> Sent: Wednesday, August 08, 2001 4:37 PM
> Subject: RE: unlink() problem
> > ... The net result is that you lose your data.
> >
> > I can't think of anyway around it except to know that you
> can't do inplace
> > editing on cygwin.
> >
> > -- John Wiersba
>
> > > >$ touch asdf
> > > >$ perl -i -pe 1 asdf
> > > >Can't do inplace edit on asdf: Permission denied.
> But using ActiveState perl,
>
> D:\home>perl -i -pe 1 asdf
> Can't do inplace edit without backup.
>
> and the file's not clobbered.
> Time to look at the perl source code.
The following seems to do the trick.
--- perl-5.6.1-1/doio.c Thu Aug 9 11:34:16 2001
+++ perl-5.6.1-1/doio.c~ Sun Dec 17 23:46:49 2000
@@ -655,7 +655,7 @@
#endif
}
else {
-#if !defined(DOSISH) && !defined(AMIGAOS) && !defined(__CYGWIN__)
+#if !defined(DOSISH) && !defined(AMIGAOS)
# ifndef VMS /* Don't delete; use automatic file versioning */
if (UNLINK(PL_oldname) < 0) {
if (ckWARN_d(WARN_INPLACE))
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^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: unlink() problem
@ 2001-08-08 13:36 Robinow, David
0 siblings, 0 replies; 6+ messages in thread
From: Robinow, David @ 2001-08-08 13:36 UTC (permalink / raw)
To: 'cygwin'
> From: John Wiersba [ mailto:John.Wiersba@medstat.com ]
> Subject: RE: unlink() problem
> Thanks for your reply, Larry. Unfortunately, this is a bad bug since the
> simple perl script below removes the original file (whoops!) since it
> assumes that if you have permission to unlink the original file, then you
> have permission to create a new file of the same name (I believe this is
> always true on unix). The net result is that you lose your data.
>
> I can't think of anyway around it except to know that you can't do inplace
> editing on cygwin.
>
> -- John Wiersba
> > >$ touch asdf
> > >$ perl -i -pe 1 asdf
> > >Can't do inplace edit on asdf: Permission denied.
But using ActiveState perl,
D:\home>perl -i -pe 1 asdf
Can't do inplace edit without backup.
and the file's not clobbered.
Time to look at the perl source code.
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: unlink() problem
2001-07-31 15:24 John Wiersba
@ 2001-07-31 16:00 ` Larry Hall (RFK Partners, Inc)
0 siblings, 0 replies; 6+ messages in thread
From: Larry Hall (RFK Partners, Inc) @ 2001-07-31 16:00 UTC (permalink / raw)
To: John Wiersba, 'cygwin'
At 06:22 PM 7/31/2001, John Wiersba wrote:
>I'm having a problem with unlink(). I've scanned the FAQ and searched some
>in the newsgroup archives for information about the following problem. I
>did find a post (see
> http://sources.redhat.com/ml/cygwin/2001-05/msg01095.html ) but no apparent
>resolution.
>
>$ touch asdf
>$ perl -i -pe 1 asdf
>Can't do inplace edit on asdf: Permission denied.
>
>What perl is doing is equivalent to:
>
>$ perl -e '
> open A, "< asdf" or die "one $!"; # open asdf for read
> unlink "asdf";
> open B, "> asdf" or die "two $!"; # open asdf for write
> while (<A>) { print B } # copy from A to B
>'
>two Permission denied at -e line 4.
>
>The problem: after the unlink(), I can't open the same filename for write
>as I can on unix. If I pause the program after unlinking asdf, it is still
>there and can be seen by ls, but can't be read by ls -l.
>
>Is there a workaround for this behavior? Is it considered a bug or is it
>just a quirk of the cygwin implementation of trying to implement unix
>filesystem semantics on top of windows?
The latter. This has been quite a day for this issue! This is the
third time it came up. Perhaps this qualifies as an FAQ now! ;-)
See my previous posts about this subject from earlier in the day:
http://www.cygwin.com/ml/cygwin/2001-07/msg01797.html
http://www.cygwin.com/ml/cygwin/2001-07/msg01774.html
There's also a related FAQ, although the message it mentions doesn't
seem to pop up anymore, which gives insight into the underlying
implementation. See:
http://www.cygwin.com/faq/faq_4.html#SEC57
Of course, the code is the "last word" on this subject in terms of the
actual implementation.
Larry Hall lhall@rfk.com
RFK Partners, Inc. http://www.rfk.com
118 Washington Street (508) 893-9779 - RFK Office
Holliston, MA 01746 (508) 893-9889 - FAX
--
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Bug reporting: http://cygwin.com/bugs.html
Documentation: http://cygwin.com/docs.html
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^ permalink raw reply [flat|nested] 6+ messages in thread
* unlink() problem
@ 2001-07-31 15:24 John Wiersba
2001-07-31 16:00 ` Larry Hall (RFK Partners, Inc)
0 siblings, 1 reply; 6+ messages in thread
From: John Wiersba @ 2001-07-31 15:24 UTC (permalink / raw)
To: 'cygwin'
I'm having a problem with unlink(). I've scanned the FAQ and searched some
in the newsgroup archives for information about the following problem. I
did find a post (see
http://sources.redhat.com/ml/cygwin/2001-05/msg01095.html ) but no apparent
resolution.
$ touch asdf
$ perl -i -pe 1 asdf
Can't do inplace edit on asdf: Permission denied.
What perl is doing is equivalent to:
$ perl -e '
open A, "< asdf" or die "one $!"; # open asdf for read
unlink "asdf";
open B, "> asdf" or die "two $!"; # open asdf for write
while (<A>) { print B } # copy from A to B
'
two Permission denied at -e line 4.
The problem: after the unlink(), I can't open the same filename for write
as I can on unix. If I pause the program after unlinking asdf, it is still
there and can be seen by ls, but can't be read by ls -l.
Is there a workaround for this behavior? Is it considered a bug or is it
just a quirk of the cygwin implementation of trying to implement unix
filesystem semantics on top of windows?
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^ permalink raw reply [flat|nested] 6+ messages in thread
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2001-08-08 12:49 unlink() problem John Wiersba
2001-08-08 12:58 ` Larry Hall (RFK Partners, Inc)
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2001-08-09 9:31 Robinow, David
2001-08-08 13:36 Robinow, David
2001-07-31 15:24 John Wiersba
2001-07-31 16:00 ` Larry Hall (RFK Partners, Inc)
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