Re: bug with for and |&

Re: bug with for and |&

[Sven Wischnowsky]

Peter Stephenson wrote:

> The problem is general to cases where a current-shell construct on the left
> of the pipeline contains an external command.  It doesn't matter what's on
> the right of the pipeline.  The code on the left seems to be executing all
> right.
> 
> % exec 3>&2
> % { ls; print Finished >&3 } |& cat
> Finished
> 
> and it hangs in zwaitjobs, waiting for the job to finish, which it never
> does.  Change `ls' to `print foo' and the problem goes away.

Rats. I still can't reproduce it, neither with (on Linux), nor without 
(on DU) the patch. So I guess there must be some kind of race
condition somewhere...


Bye
 Sven


--
Sven Wischnowsky                         wischnow@informatik.hu-berlin.de

RE: bug with for and |&

[Andrej Borsenkow]

>
> Peter Stephenson wrote:
>
> > The problem is general to cases where a current-shell construct
> on the left
> > of the pipeline contains an external command.  It doesn't matter what's on
> > the right of the pipeline.  The code on the left seems to be executing all
> > right.
> >
> > % exec 3>&2
> > % { ls; print Finished >&3 } |& cat
> > Finished
> >
> > and it hangs in zwaitjobs, waiting for the job to finish, which it never
> > does.  Change `ls' to `print foo' and the problem goes away.
>
> Rats. I still can't reproduce it, neither with (on Linux), nor without
> (on DU) the patch. So I guess there must be some kind of race
> condition somewhere...
>


Sorry for "me too", but neither do I. It works here all right. It may well be
some uninitialized variable.

-andrej

Re: bug with for and |&

[Peter Stephenson]

The problem is general to cases where a current-shell construct on the left
of the pipeline contains an external command.  It doesn't matter what's on
the right of the pipeline.  The code on the left seems to be executing all
right.

% exec 3>&2
% { ls; print Finished >&3 } |& cat
Finished

and it hangs in zwaitjobs, waiting for the job to finish, which it never
does.  Change `ls' to `print foo' and the problem goes away.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
Cambridge Silicon Radio, Unit 300, Science Park, Milton Road,
Cambridge, CB4 0XL, UK                          Tel: +44 (0)1223 392070

Re: bug with for and |&

[Peter Stephenson]

> On Dec 18,  2:22pm, Akim Demaille wrote:
> }
> } /tmp % for i in 1 2
> } do                 
> } ls                   
> } done |& tee /tmp/foof
> } # I have to C-c C-c to stop it.
> } # s/|&/|/ makes it work properly.
> 
> For what it's worth, I'm *not* able to reproduce this here.
> 
> The difference may be that I have Sven's patch from zsh-workers/13247 applied

That doesn't make any difference to me.  The extra `&' is certainly the
problem.  You can work around it by sticking 2>&1 after the ls; 2>&1 after
the `done' has the same effect as the original.  There's problem some
difficulty with the logic in execcmd().

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
Cambridge Silicon Radio, Unit 300, Science Park, Milton Road,
Cambridge, CB4 0XL, UK                          Tel: +44 (0)1223 392070