sandbox.rb

# ==============
# Spell: Sandbox
# ==============

# Execute untrusted code in a safe environment.

def sandbox(&code)
  proc {
    $SAFE = 2
    yield
  }.call
end

begin
  sandbox { File.delete 'a_file' }
rescue Exception => ex
  ex  # => #<SecurityError: Insecure operation `delete' at level 2>
end

# For more information: http://www.pragprog.com/titles/ppmetr/metaprogramming-ruby