[Fwd: Re: job control for the es shell]

[Olaf Rogalsky <Olaf.Rogalsky@physik.uni-erlangen.de>]

Paul Haahr wrote:
>   (1) Correct job control in es requires some notion of (internal-to-es)
>       thread (or process or ...) that can be stopped and started.
Indeed. The only stoppable objects in my patch are forked processes 
(process groups).

>   (2) The right way to implement threads in es is using first class
>       continuations (e.g., call/cc).
It would be much easier, if unix had rich return values. Then a simple
fork will allmost do the trick. Allmost ... 

> What do I mean by ``correct''?  Basically, that es commands can be
> seemlessly interrupted and restarted regardless of whether they're
> running within the shell or in forked processes.  I only tried your
> patch very quickly, but it doesn't appear to satisfy that criteria.
No, it doesn't. Unfortunately.

> For examples, try interrupting (& restarting) things like
>   while true { sleep 1 }
>   while true { echo t }
>   x = `{ date; sleep 100; date }
How do other shells do job control on those examples?
Ksh88: 
  Ksh simply disables job control for command sequences! A simple approach,
  but clean and predictable.
bash2.0: 
  Pressing ^Z or ^C has the expected result on all external processes in a
  sequence of commands. Any intenal (to bash) command is interrupted and not
  restartable.
  But there are bugs, too. Try to stop and then kill the following:
    echo $(sleep 9999|sleep 9999)
mypatch:
  I have put a new version of the patch with several bugfixes on my web page:
  http://theorie1.physik.uni-erlangen.de/rogalsky/es
  It's still not fully tested, but at least the first two examples of yours 
  are now interruptable. The last example only examplifies, that my patch
  isn't ``correct''.

Thanks for your tests,
    Olaf


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