ref: 5ee0d9a4171ae5b6873a40416a8148a07a9a6e70
dir: /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)