Update:
I added a quick language def which outlines all the functions, and a new example "knob.rb" which is another example to use.

I have converted the 22 examples included with openscad into RubyScad scripts. These use just about every command in the openscad language and will detail the syntax. I will highlight some of the features below / some of the common pitfalls when migrating.

Basic Use:
Install Ruby 1.9.3 > (in ubuntu repos, easy windows and mac auto install): ruby-lang.org/en/
Install RubyGems: rubygems.org/
Run: gem install rubyscad

Super Simple:
in a blank ruby document i.e. test.rb:

  require "rubyscad"



  include RubyScad

  translate(x: 5)

  cube(size: 6)

then simple run this from command line:
ruby test.rb

this will print the output to the command line which can be piped to a file OR
run the file with a string as the first argument::
ruby test.rb "output.scad"

which will create "output.scad" file in the same directory

Using A Module

require "rubyscad"

module Test

  extend RubyScad

   translate(v:[1,2,3]) {

    union {

      sphere(r: 3, center:true)

      cube(size:3, center:true)

    }

   }

end

Using A Class

require "rubyscad"

class TestClass

  include RubyScad

  def initialize(args={})

     @size = args.fetch(:size, 1)

   end

   def render()

      cube(size: @size)

   end

end

TestClass.new.render

To use an existing library:

require "rubyscad"

module WriteTest

  extend RubyScad

  use "Write.scad"

  def self.writecylinder(args={})

     format_command "writecylinder(%s);", args

  end

  writecylinder(text: "test", where: [0,0,0])

end

To output any string directly to openscad use:
format_output("string")

Common Pitfalls:
-When using a function it is general named the same as the openscad function i.e. cube, sphere... with the exception of the include function which is "scad_include" so as not to interfere with ruby’s function of the same name

-Functions always accept a hash for their arguments so all calls will look like: cube(size: 6, center:true) which means the following is ILLEGAL: translate([1,2,3]) and must be converted to translate(v:[1,2,3] or optionally translate(x:1,y:2,z:3). Exceptions to this are "echo" which takes any number of arguments, and create an echo statement in openscad i.e. echo 4, 5, "test". "use", and "scad_include" take one string i.e. use "write.scad".

-To set global '$' variables use the associated function "$fa = 4" becomes "fa 4", "$fs = 6" becomes "fs 6", and "$fn = 12" becomes "fn 12"

That’s the high level overview, look at the examples for more details, or leave a comment if I need to clarify something.