Re: tail and win file handling

Re: tail and win file handling

[Paul Haas]

Larry Hall wrote:

> the file deleted by "rm" isn't deleted really until it's closed, which
> won't happen until 'tail' ends.  This is the way Windows works.  There's
> not much to be done about it (at least not in Cygwin).  Believe me,
> we've tried.

Here is a really ugly kludge to deal with a really ugly file system.

I'm sure I read about this sort of kludge before, so the idea is certainly
not original.

-------Cut here------
#!/usr/bin/perl -w
# this acts sort of like tail -f, but doesn't keep the
# open.  It is designed for non-unix systems where open files
# can't be deleted.
# It mindlessly shows the last 512 bytes of the file on startup
# rather than the last 10 lines.
#
#  Paul Haas, May 19, 2004
my $file = shift;
open(TF,$file) || die "Reading $file $!";
seek(TF,-512,2);
@lines=<TF>;
my $curpos=tell(TF);
close(TF);
print @lines;
sleep 1;
while(-r $file ) {
  open(TF,$file) || die "Rereading $file $!";
  seek(TF,$curpos,0);
  @lines=<TF>;
  $curpos = tell(TF);
  print @lines;
  close(TF);
  sleep 1;
}


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Re: tail and win file handling

[Larry Hall]

At 01:08 PM 5/18/2004, you wrote:
>I can't change the application unfortunately, if I
>could I'd have it only log interesting stuff rather
>than the garbage it does.
>
>Is it worth trying maybe to link the file and tail the
>link ? or mess with a tee command ??


I guess I'm unclear on what you're doing and what's creating/removing
the file you're interested in and how it's being done.  The above ideas 
may work in your situation.  I don't know.  For the example you posted,
the file deleted by "rm" isn't deleted really until it's closed, which
won't happen until 'tail' ends.  This is the way Windows works.  There's
not much to be done about it (at least not in Cygwin).  Believe me, we've
tried.


--
Larry Hall                              http://www.rfk.com
RFK Partners, Inc.                      (508) 893-9779 - RFK Office
838 Washington Street                   (508) 893-9889 - FAX
Holliston, MA 01746                     


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Re: tail and win file handling

[C Wells]

I can't change the application unfortunately, if I
could I'd have it only log interesting stuff rather
than the garbage it does.

Is it worth trying maybe to link the file and tail the
link ? or mess with a tee command ??

--- Larry Hall <cygwin-lh@cygwin.com> wrote:
> re tail and win file handles.

> Your going to have to use a different file name. 
> Windows doesn't 
> support the same semantics in this case.  The
> emulation Cygwin provides
> is as close as you're going to get (which ain't that
> close but... ;-) ).
> 


	
		
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Re: tail and win file handling

[Larry Hall]

At 09:31 AM 5/18/2004, you wrote:
>I am sorry if this has been covered before, but I was
>wondering if there is work around (probably not ;-(
>
>In unix you can do the following
>tail -f /somefile
>in another session
>rm -f /somefile
>echo OK > /somefile
>
>of course the tail stops working, but the file is
>recreated
>
>On a cygwin box
>tail -f c:/somefile
>in another session
>rm -f c:/somefile
>echo OK > c:/somefile
>'Access is denied'
>
>So obviously the tail puts a lock on the file,
>preventing an application from creating a new one,
>which in my case breaks the application. Any thoughts
>about how work around this, given I need to tail the
>file ? 


Your going to have to use a different file name.  Windows doesn't 
support the same semantics in this case.  The emulation Cygwin provides
is as close as you're going to get (which ain't that close but... ;-) ).


--
Larry Hall                              http://www.rfk.com
RFK Partners, Inc.                      (508) 893-9779 - RFK Office
838 Washington Street                   (508) 893-9889 - FAX
Holliston, MA 01746                     


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tail and win file handling

[C Wells]

I am sorry if this has been covered before, but I was
wondering if there is work around (probably not ;-(

In unix you can do the following
tail -f /somefile
in another session
rm -f /somefile
echo OK > /somefile

of course the tail stops working, but the file is
recreated

On a cygwin box
tail -f c:/somefile
in another session
rm -f c:/somefile
echo OK > c:/somefile
'Access is denied'

So obviously the tail puts a lock on the file,
preventing an application from creating a new one,
which in my case breaks the application. Any thoughts
about how work around this, given I need to tail the
file ?

Thanks



	
		
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