From: Robert Klemme <shortcutter@...>
Date: 2009-09-08T04:20:05+09:00
Subject: Re: Opinion: Scripting in a Ruby program

On 07.09.2009 18:57, Tristan Shelton wrote:
> Thank you all for your input. I apologize, as it seems I caused some 
> confusion with my original post. I'm looking for something that allows 
> the user to perform a few simple operations in a sandbox context, rather 
> than a framework for programmers to build upon. Something that would 
> allow me to compile the main program with ruby2exe and then load -- and 
> reload without interrupting the execution of the main program -- small 
> bits of script from an external source (e.g. a file) with.
> 
> To bring things into context I have a game in which I would like certain 
> objects to be scriptable to some degree. Nothing extremely involved; 
> just a few methods, properties, and control structures. So essentially a 
> scripting "language" that can be provided a simple subset of the main 
> program's functionality in a sandbox context that doesn't allow file and 
> network I/O, shell access, and all those other nifty things Ruby 
> normally does.
> 
> Something comparable to Unrealscript or Actionscript (which as I 
> understand is essentially Javascript) would work fine, I'm just curious 
> how one would go about implementing such functionality in Ruby. Any 
> further suggestions are welcome, and no one solution may be best, but 
> I'm interested to know what's out there and what's possible.

For one, you can do something like this:

class Shell
   class Context
     # custom commands for user code
     def move
       puts "moving..."
     end
   end

   # interactive commands
   def load(file)
     c = Context.new
     c.instance_eval(File.read(file))
     nil
   end
end

Then you can have a file which contains "move" on a line and you'll see 
the move printed.

There is also $SAFE:
http://ruby-doc.org/docs/ProgrammingRuby/html/taint.html#S1

Typically you set up an environment and then start another thread which 
restricts $SAFE to provide the sandbox environment.

Also, Try Ruby's source should contain sandboxing techniques as well 
(see recent posts).

Kind regards

	robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/