ref: 7d5831d86dbce4d15c09dea4ff7b8ab1dda0a30a
dir: /src/lua/test/env.lua/
-- read environment variables as if they were global variables
local f=function (t,i) return os.getenv(i) end
setmetatable(getfenv(),{__index=f})
-- an example
print(a,USER,PATH)