HowTo: Write Modules

Note: If you plan to integrate your module into LuCI, you should read the Module Reference before.

This tutorial describes how to write your own modules for the LuCI WebUI. For this tutorial we refer to your LuCI installation directory as lucidir (/usr/lib/lua/luci if you are working with an installed version) and assume your LuCI installation is reachable through your webserver via /cgi-bin/luci.

If you are working with the development environment replace lucidir with /path/to/your/luci/checkout/applications/myapplication/luasrc (this is a default empty module you can use for your experiments) and your LuCI installation can probably be reached via  http://localhost:8080/luci/ after you ran make runhttpd.

Show me the way (The dispatching process)

To write a module you need to understand the basics of the dispatching process in LuCI. LuCI uses a dispatching tree that will be built by executing the index-Function of every available controller. The CGI-environment variablePATH_INFO will be used as the path in this dispatching tree, e.g.: /cgi-bin/luci/foo/bar/baz will be resolved to foo.bar.baz

To register a function in the dispatching tree, you can use the entry-function of luci.dispatcher. entry takes 4 arguments (2 are optional):

entry(path, target, title=nil, order=nil)

• path is a table that describes the position in the dispatching tree: For example a path of {"foo", "bar", "baz"} would insert your node in foo.bar.baz.
• target describes the action that will be taken when a user requests the node. There are several predefined ones of which the 3 most important (call, template, cbi) are described later on on this page
• title defines the title that will be visible to the user in the menu (optional)
• order is a number with which nodes on the same level will be sorted in the menu (optional)

You can assign more attributes by manipulating the node table returned by the entry-function. A few example attributes:

• i18n defines which translation file should be automatically loaded when the page gets requested
• dependent protects plugins to be called out of their context if a parent node is missing
• leaf stops parsing the request at this node and goes no further in the dispatching tree
• sysauth requires the user to authenticate with a given system user account

It's all about names (Naming and the module file)

Now that you know the basics about dispatching, we can start writing modules. But before you have to choose the category and name of your new digital child.

We assume you want to create a new application "myapp" with a module "mymodule".

So you have to create a new subdirectory lucidir/controller/myapp with a file mymodule.lua with the following content:

module("luci.controller.myapp.mymodule", package.seeall)function index()end

The first line is required for Lua to correctly identify the module and create its scope. The index-Function will be used to register actions in the dispatching tree.

Teaching your new child (Actions)

So it is there and has a name but it has no actions.

We assume you want to reuse your module myapp.mymodule that you begun in the last step.

Actions

Reopen lucidir/controller/myapp/mymodule.lua and just add a function to it so that its content looks like this example:

module("luci.controller.myapp.mymodule", package.seeall)function index()entry({"click", "here", "now"}, call("action_tryme"), "Click here", 10).dependent=false
endfunction action_tryme()luci.http.prepare_content("text/plain")luci.http.write("Haha, rebooting now...")luci.sys.reboot()
end

And now type /cgi-bin/luci/click/here/now ( http://localhost:8080/luci/click/here/now if you are using the development environment) in your browser.

You see these action functions simple have to be added to a dispatching entry.

As you might or might not know: CGI specification requires you to send a Content-Type header before you can send your content. You will find several shortcuts (like the one used above) as well as redirecting functions in the module luci.http

Views

If you only want to show the user a text or some interesting familiy photos it may be enough to use a HTML-template. These templates can also include some Lua code but be aware that writing whole office suites by only using these templates might be called "dirty" by other developers.

Now let's create a little template lucidir/view/myapp-mymodule/helloworld.htm with the content:

<%+header%>
<h1><%:Hello World%></h1>
<%+footer%>

and add the following line to the index-Function of your module file.

entry({"my", "new", "template"}, template("myapp-mymodule/helloworld"), "Hello world", 20).dependent=false

Now type /cgi-bin/luci/my/new/template ( http://localhost:8080/luci/my/new/template if you are using the development environment) in your browser.

You may notice those fancy <% %>-Tags, these are markups? used by the LuCI template processor. It is always good to include header and footer at the beginning and end of a template as those create the default design and menu.

CBI models

The CBI is one of the uber coolest features of LuCI. It creates a formular based user interface and saves its contents to a specific UCI config file. You only have to describe the structure of the configuration file in a CBI model file and Luci does the rest of the work. This includes generating, parsing and validating a XHTML form and reading and writing the UCI file.

So let's be serious at least for this paragraph and create a real pratical example lucidir/model/cbi/myapp-mymodule/netifaces.lua with the following contents:

m = Map("network", "Network") -- We want to edit the uci config file /etc/config/networks = m:section(TypedSection, "interface", "Interfaces") -- Especially the "interface"-sections
s.addremove = true -- Allow the user to create and remove the interfaces
function s:filter(value)return value ~= "loopback" and value -- Don't touch loopback
end
s:depends("proto", "static") -- Only show those with "static"
s:depends("proto", "dhcp") -- or "dhcp" as protocol and leave PPPoE and PPTP alonep = s:option(ListValue, "proto", "Protocol") -- Creates an element list (select box)
p:value("static", "static") -- Key and value pairs
p:value("dhcp", "DHCP")
p.default = "static"s:option(Value, "ifname", "interface", "the physical interface to be used") -- This will give a simple textboxs:option(Value, "ipaddr", translate("ip", "IP Address")) -- Ja, das ist eine i18n-Funktion ;-)s:option(Value, "netmask", "Netmask"):depends("proto", "static") -- You may remember this "depends" function from abovemtu = s:option(Value, "mtu", "MTU")
mtu.optional = true -- This one is very optionaldns = s:option(Value, "dns", "DNS-Server")
dns:depends("proto", "static")
dns.optional = true
function dns:validate(value) -- Now, that's nifty, eh?return value:match("[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+") -- Returns nil if it doesn't match otherwise returns match
endgw = s:option(Value, "gateway", "Gateway")
gw:depends("proto", "static")
gw.rmempty = true -- Remove entry if it is emptyreturn m -- Returns the map

and of course don't forget to add something like this to your module's index-Function.

entry({"admin", "network", "interfaces"}, cbi("myapp-mymodule/netifaces"), "Network interfaces", 30).dependent=false

There are many more features, see the CBI reference and the modules shipped with LuCI.

Reference: LuCI Modules

Categories

The LuCI modules are divided into several category directories, namely:

• applications (Single applications or plugins for other modules or applications)
• i18n (Translation files)
• libs (Independent libraries)
• modules (Collections of applications)
• themes (Frontend themes)

Each module goes into a subdirectory of any of this category-directories.

Module directory

The contents of a module directory are as follows:

Makefile

This is the module's makefile. If the module just contains Lua sourcecode or resources then the following Makefile should suffice.

include ../../build/config.mk
include ../../build/module.mk

If you have C(++) code in your module your Makefile should at least contain the following things.

include ../../build/config.mk
include ../../build/gccconfig.mk
include ../../build/module.mkcompile:# Commands to compile and link your C-code# and to install them under the dist/ hierarchyclean: luaclean# Commands to clean your compiled objects

src

The src directory is reserved for C sourcecode.

luasrc

luasrc contains all Lua sourcecode files. These will automatically be stripped or compiled depending on the Make target and are installed in the LuCI installation directory.

lua

lua is equivalent to luasrc but containing Lua files will be installed in the Lua document root.

htdocs

All files under htdocs will be copied to the document root of the target webserver.

root

All directories and files under root will be copied to the installation target as they are.

dist

dist is reserved for the builder to create a working installation tree that will represent the filesystem on the target machine. DO NOT put any files there as they will get deleted.

ipkg

ipkg contains IPKG package control files, like preinst, posinst, prerm, postrm. conffiles. See IPKG documentation for details.

OpenWRT feed integration

If you want to add your module to the LuCI OpenWRT feed you have to add several sections to the contrib/package/luci/Makefile.

For a Web UI applications this is:

A package description:

define Package/luci-app-YOURMODULE$(call Package/luci/webtemplate)DEPENDS+=+some-package +some-other-packageTITLE:=SHORT DESCRIPTION OF YOURMODULE
endef

A package installation target:

define Package/luci-app-YOURMODULE/install$(call Package/luci/install/template,$(1),applications/YOURMODULE)
endef

A module build instruction:

ifneq ($(CONFIG_PACKAGE_luci-app-YOURMODULE),)PKG_SELECTED_MODULES+=applications/YOURMODULE
endif

A build package call:

$(eval $(call BuildPackage,luci-app-YOURMODULE))