如何在LuCI里添加print？

这个方式是从openwrt的maillist里找到的，适合那些想修改luci，但是对lua语言又不熟悉的人。

大意如下：

某人问在LuCI里添加print("hello")，出现错误。为啥？

attempt to call global 'print' (a nil value)

然后，下面有个人回复说，需要在文件开头添加这么一行：

local print = print

因为这个文件是一个module，它调用了module函数。详细信息，可以参考Lua手册

原文如下：

Hi all,

when i add above

    'print("hello")'  in /usr/lib/lua/luci/model/uci.lua

got follow error:

/usr/lib/lua/luci/dispatcher.lua:448: Failed to execute call dispatcher
target for entry '/servicectl/restart/firewall'.
The called action terminated with an exception:
/usr/lib/lua/luci/model/uci.lua:71: attempt to call global 'print' (a nil
value)
stack traceback:
[C]: in function 'assert'
/usr/lib/lua/luci/dispatcher.lua:448: in function 'dispatch'
/usr/lib/lua/luci/dispatcher.lua:195: in function 

why cannot use print to print some value?

thanks all!

elvis

--------------------------------------------------------------------------------------

You need to define it first at the top of the file:

	diff --git a/libs/core/luasrc/model/uci.lua b/libs/core/luasrc/model/uci.lua
	index a394563..f513c77 100644
	--- a/libs/core/luasrc/model/uci.lua
	+++ b/libs/core/luasrc/model/uci.lua
	@@ -27,6 +27,7 @@ local os    = require "os"
	 local uci   = require "uci"
	 local util  = require "luci.util"
	 local table = require "table"
	+local print = print

Why? It's because of the following function call:

	module "luci.model.uci"

For the details, read the fine Lua manual[1]. BTW, it's better to use file for
debugging output, since you can easily loose some hairs with stdout/stderr
debugging in the Luci development :-)

1. http://www.lua.org/manual/5.1/manual.html#pdf-module