Re: why does "jobs | wc" not work?

[Dominik Vogt <dominik.vogt@gmx.de>]

On Tue, Nov 26, 2002 at 11:09:15AM +0000, Peter Stephenson wrote:
> Dominik Vogt wrote:
> > There seems to be a strange bug with the jobs command in
> > zsh-4.0.4.  It seems that the output of the jobs command refuses
> > to go into a pipe.
> 
> This isn't strictly a bug, but there's a workaround in the 4.1 code.
> 
> In zsh
> 
> jobs | anything
> 
> causes the shell to fork for the left hand side of the pipeline.

Um, why must builtin commands run in a subshell?  I would have
naively thought commands like "echo something | ..." would just
run in the current shell.  Spawning a subshell sounds a bit
inefficient.

> This
> is then no longer the shell with the job control, hence doesn't show any
> jobs.  Other shells fork the `anything' and run `jobs' in the current
> shell.  We deliberately don't do that because we like to be able to do
> 
> anything | read foo
> 
> to get the variable $foo set in the current shell (and all sorts of similar
> examples).
> 
> In 4.1, we use the obvious workaround:  remember that we're in a subshell
> of an interactive shell and keep a fossilized list of the jobs.

Obvious, maybe, but it still sounds wrong in my ears.

> This can
> mean that the task list isn't up to date at the point where the jobs
> command is actually run --- though there are obvious races when
> background jobs terminate anyway, so I don't think that's a major
> concern.

Bye

Dominik ^_^  ^_^