Re: suspend (^Z) behavior while a function is running is unclear

[Vincent Lefevre <vincent@xxxxxxxxxx>]

On 2012-02-20 09:41:00 -0800, Bart Schaefer wrote:
> On Feb 20,  4:35pm, Peter Stephenson wrote:
> > Subject: Re: suspend (^Z) behavior while a function is running is unclear
> >
> > On Mon, 20 Feb 2012 17:09:45 +0100
> > Vincent Lefevre <vincent@xxxxxxxxxx> wrote:
> > > Now I'm thinking whether there should be an option to control that.
> > > Indeed, some functions may fail to work correctly if they are suspended
> > > in such a way. Some functions or { list } could be marked as not
> > > backgroundable, e.g. by setting an option at the beginning, in which
> > > case the ^Z could be ignored.
> 
> This is already partly in place:
> 
> 2011-08-14  Barton E. Schaefer  <schaefer@xxxxxxx>
> 
>         * 29677: Src/exec.c, Src/signals.c, Src/zsh.h: flag jobs that are
>         builtins running in the current shell, and if they control a
>         pipeline, do not allow the external processes in that pipeline to
>         become suspended when the foreground shell cannot suspend.
> 
> torch% foreach foo (a b c) { sleep 5 } | :  
> zsh: job can't be suspended

However if the command outputs something, one loses the output.

> > Useful, but I'm not sure an option is the right way of doing this... I
> > should think you'd want to do something like:
> > 
> > {
> >   stty susp undef
> >   ...
> > } always {
> >   stty susp '^z'
> > }
> 
> I'm not sure that's the right semantics.  Does one want to disable the
> tty suspend character or just ingore the TSTP signal?  What if "emacs"
> in the original example was replaced by running another shell?

The ^Z should affect only the other shell. So, I think this is OK.
But with the encapsulation (to save typing), this is very limited.
For instance, one cannot use a complex command like:

  nosuspend for i in ...

or even use a function after "nosuspend".

-- 
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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