Re: gush -> plush

[Eli Barzilay <eli@barzilay.org>]

On Nov 18, Paul Graunke wrote:
> The gush project, which provided a simple unix shell running under
> guile, is in limbo now.  The only thing interesting about it is that
> scheme "shell scripts" are loaded into the same guile interpeter.
> Their OS like protections appear to be, "Please don't poke me too
> hard."  Here's a first cut a replacing gush with a plt-scheme
> version, that hopefully does better on the protections.  It's just
> something I hacked together in a few hours this afternoon, so don't
> expect scsh.  It's more for interactive use with plain old scheme
> programs for more complex tasks.

I think that there are three independent things here:

1. There is the actual scripting support that means a lot of scsh
   functionality imported into MzScheme.  I think that one change for
   that would be to redesign the system functions so they will return
   an actual process object that will allow much more control than the
   current list of return values.

2. For this gush-like thing there is the safe evaluation that is
   needed.

3. Some interactive shell support.

Any of these three things will be useful by itself.  I have some hacks
that does these things partially:

1. I started doing this, but it seems like there are things on higher
   priority so it's on hold for now.  Basically, I had a new function
   in port.c that will fork and return a subprocess object, something
   similar to process*/ports that returns a process.  Then there is
   some Scheme source that uses this to implement the current
   functions using the new one, and adds more scsh-like stuff: I have
   support for starting processes either in the foreground or in the
   background, piping, using symbols as paths etc.  One cute thing was
   to find a way to have threads with return values and that get i/o
   ports when they start, and the result was that you can use, in a
   single pipeline, both system processes and Scheme threads.

2. For this point I had once an implementation of a Scheme server
   (actually a Swindle server, but there wasn't any Swindle-specific
   code there) that allowed users to telnet into and get their own
   REPL that the single server provides.  The safe execution is
   provided by different evaluation threads and namespaces.

3. Finally, for user-interaction, the telnet server thing would
   respond to some telnet sequences, so if you would hit ^Z the
   expression that was evaluating was pushed to the background etc.

I'll try to see if there is these things still work.

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                  http://www.barzilay.org/                 Maze is Life!