Mail Archives: cygwin/2001/08/08/15:58:59
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 AT rfk DOT 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 AT rfk DOT 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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