Run Ruby from LuaJIT

test.lua

#!/usr/bin/env luajit

local ffi  = require 'ffi'
local cast = ffi.cast
local cdef = ffi.cdef
local load = ffi.load

local libruby = load '/usr/lib/libruby.so'

cdef[[
  typedef unsigned long VALUE;
  void ruby_init(void);
  VALUE rb_eval_string(const char *);
  int ruby_cleanup(volatile int ex);
]]

local rbcode = cast('char *', 'puts (1..20).inject(:lcm)')

libruby.ruby_init()
libruby.rb_eval_string(rbcode)
libruby.ruby_cleanup(0)