Disable CTRL G

[Peter Andersson]

Sean,

I can see the advantages of being able to disable the JCL menu. I don't
like the idea of having the restricted shell callbacks handle JCL
commands. 

Since you would disable the JCL quit option for the same reasons you
would disable ^C, I still believe +Bi should switch them both off. I'd
choose to introduce a new start option to give ^G a shell restart
behaviour (like oldshell) instead of JCL mode, like you suggest. You'd
have the possibility to force all interaction from the shell to go via
the prompt or you could choose to have JCL mode enabled but without the
risky 'q' option. Sounds ok?

  /Peppe


Sean Hinde wrote:
> 
> Peter,
> 
> > The restricted shell mode + "ignore break" is indeed there for
> > protection against simple operator mistakes. Pressing 'q' and stopping
> > the node in e.g. an attempt to exit the job control (JCL) mode, could
> > very well happen by mistake.
> 
> Indeed. It has.
> 
> >
> > So, speaking of mistakes, not being able to disable the JCL quit option
> > - that's one for sure. Bugger.
> >
> > Here's my suggestion: The ignore break flag, erl +Bi, is already used
> > for disabling ^C break/stop of the system. Let's have the same flag
> > also
> > disable any shell shortcut for stopping the system (that'd be the JCL
> > quit option). After all, it's the same kind of "halt by accident" from
> > the shell that we'd be trying to avoid. Do you agree? If so, I'll get
> > to
> > it.
> 
> I think that there is a distinction between "Safe" JCL functions and
> "Unsafe" JCL functions. I would categorise safe ones as:
> 
> c
> i
> k
> j
> s
> ? | h
> 
> and unsafe as r [node] and q
> 
> Other peoples definitions of safe/unsafe might be different. I guess
> the ultimate solution would be to be able to define a function in the
> restricted shell callback to allow or deny each of these options or
> even to drop back to an old_shell like mode where CTRL-G just gives you
> a new shell if you have buggered up the old one in some way.
> 
> A minimal solution could well be to link this to the +Bi option, or
> perhaps better to provide a +G [i] option.
> 
> > Until it's fixed, you know ^G in a primitive Erlang shell (erl
> > -oldshell) will only restart the current evaluator, not bring up the
> > JCL
> > menu? So you get no halt() shortcuts when using a restricted oldshell
> > ignoring break (erl -oldshell -stdlib restricted_shell <mod> +Bi).
> 
> Actually this shell looks OK for operator usage - I quite like the fact
> that multiline commands do not give you back the 1> prompt until they
> are terminated. Alternatively this might lead to more confusion ("The
> shell has died, I'll have to restart the node!").
> 
> Let's go for some sensible way to neuter CTRL-G and I'll experiment
> with old_shell in the meantime.
> 
> Thanks very much,
> 
> Sean