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<!-- Module User's Guide -->

<chapter>

    <title>&adminguide;</title>

    <section>
	<title>Overview</title>
	<para>
		This module allows executing Lua scripts from config file, implementing
		the KEMI framework and exporting Lua module 'KSR'.
	</para>
	<para>
		To read more about KEMI exports and available KSR submodules, see:
    	<itemizedlist>
		    <listitem>
			<para>
				<ulink url="https://kamailio.org/docs/tutorials/devel/kamailio-kemi-framework/">https://kamailio.org/docs/tutorials/devel/kamailio-kemi-framework/</ulink>
			</para>
		    </listitem>
    	</itemizedlist>
	</para>
	<para>
		Note: to have the old Lua module 'sr' available, load the 'app_lua_sr'
		&kamailio; module.
	</para>
	<para>
		Lua (http://www.lua.org) is a fast and easy to embed scripting
		language. Exported API from SIP router to Lua is documented in the
		dokuwiki.
	</para>
	<para>
		The module has two Lua contexts:
    	<itemizedlist>
	    <listitem>
		<para>
			<emphasis>first</emphasis> is used for functions lua_dofile()
			and lua_dostring().
		</para>
	    </listitem>
	    <listitem>
		<para>
		    <emphasis>second</emphasis> is used for function lua_run()
			and parameter 'load'. Therefore lua_run() cannot execute functions
			from scripts loaded via lua_dofile() in config. This is kind of
			caching mode, avoiding reading file every time, but you must be sure
			you do not have something that is executed by default and requires
			access to SIP message. This is also the context used with KEMI
			framework.
		</para>
	    </listitem>
    	</itemizedlist>
	</para>
    </section>
    <section>
	<title>Dependencies</title>
	<section>
	    <title>&kamailio; Modules</title>
	    <para>
		The following modules must be loaded before this module:
	    	<itemizedlist>
		    <listitem>
			<para>
			    <emphasis>none</emphasis>.
			</para>
		    </listitem>
	    	</itemizedlist>
	    </para>
	</section>
	<section>
	    <title>External Libraries or Applications</title>
	    <para>
		The following libraries or applications must be installed before running
		&kamailio; with this module loaded:
	    	<itemizedlist>
		    <listitem>
			<para>
			    <emphasis>liblua5.1-dev</emphasis> - Lua devel library.  Versions 5.2, 5.3 and 5.4 also work.
			</para>
		    </listitem>
	    	</itemizedlist>
			<para>
			    This module can be compiled against LuaJIT compiler (instead of
			    standard Lua). Then this library is needed:
			    <itemizedlist>
				    <listitem>
				    <emphasis>libluajit-5.1-dev</emphasis> - LuaJIT devel library.
				    </listitem>
				</itemizedlist>
				<para>
				    To enable that, LUAJIT variable has to be set.
					<example>
					    <title>Build against LuaJIT libraries</title>
					E.g: $ LUAJIT="yes" make modules modules=modules/app_lua
					</example>
			    (Warning: LuaJIT version is 5.1, so scripts prepared for higher Lua versions
			    may not work with LuaJIT)
				</para>
			</para>
	    </para>
	</section>
    </section>
    <section>
	<title>Parameters</title>
	<section id="app_lua.p.load">
	    <title><varname>load</varname> (string)</title>
	    <para>
			Set the path to the Lua script to be loaded at startup. Then you
			can use lua_run(function, params) to execute a function from the
			script at runtime.  The script can be in Lua-source or bytecode.
	    </para>
	    <para>
		<emphasis>
		    Default value is <quote>null</quote>.
		</emphasis>
	    </para>
	    <example>
		<title>Set <varname>load</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("app_lua", "load", "/usr/local/etc/kamailio/lua/myscript.lua")
...
</programlisting>
	    </example>
	</section>

	<section id="app_lua.p.reload">
	    <title><varname>reload</varname> (boolean)</title>
	    <para>
			If reload is 1 enables the ability to reload the
			scripts using the RPC app_lua.reload command. To disable reload
			feature, set this parameter to 0.
	    </para>
	    <para>
		<emphasis>
		    Default value is <quote>1 (on)</quote>.
		</emphasis>
	    </para>
	    <example>
		<title>Set <varname>reload</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("app_lua", "reload", 0)
...
</programlisting>
	    </example>
	</section>

	<section id="app_lua.p.log_mode">
	    <title><varname>log_mode</varname> (int)</title>
	    <para>
			Control what is printed in log messages. If bit 1 is set, then
			the module prints debug messages for each KEMI export.
	    </para>
	    <para>
		<emphasis>
		    Default value is <quote>0</quote>.
		</emphasis>
	    </para>
	    <example>
		<title>Set <varname>log_mode</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("app_lua", "log_mode", 1)
...
</programlisting>
	    </example>
	</section>

	</section>

    <section>
	<title>Functions</title>
 	<section id="app_lua.f.lua_dotfile">
	    <title>
		<function moreinfo="none">lua_dofile(path)</function>
	    </title>
	    <para>
		Execute the Lua script stored in 'path'. The parameter can be
		a string with pseudo-variables evaluated at runtime.
	    </para>
		<example>
		<title><function>lua_dofile</function> usage</title>
		<programlisting format="linespecific">
...
lua_dofile("/usr/local/etc/kamailio/lua/myscript.lua");
...
</programlisting>
	    </example>
	</section>

 	<section id="app_lua.f.lua_dostring">
	    <title>
		<function moreinfo="none">lua_dostring(script)</function>
	    </title>
	    <para>
		Execute the Lua script stored in parameter. The parameter can be
		a string with pseudo-variables.
	    </para>
		<example>
		<title><function>lua_dostring</function> usage</title>
		<programlisting format="linespecific">
...
if(!lua_dostring("KSR.log([[err]], [[----------- Hello World from $fU\n]])"))
{
    xdbg("SCRIPT: failed to execute lua script!\n");
}
...
</programlisting>
	    </example>
	</section>

	<section id="app_lua.f.lua_run">
	    <title>
		<function moreinfo="none">lua_run(func [, params])</function>
	    </title>
	    <para>
		Execute the Lua function 'func' giving 'params' as parameters. There
		can be up to 3 string parameters after 'func' (overall, max 4 params,
		first is the function). The function must exist in the Lua
		script loaded at startup via parameter 'load'. Parameters can be
		strings with pseudo-variables that are evaluated at runtime.
	    </para>
		<example>
		<title><function>lua_run</function> usage</title>
		<programlisting format="linespecific">
...
if(!lua_run("sr_append_fu_to_reply")) {
    xdbg("SCRIPT: failed to execute lua function!\n");
}
...
lua_run("lua_func0");
lua_run("lua_func1", "$rU");
lua_run("lua_func2", "$rU", "2");
lua_run("lua_func3", "$rU", "2", "$si");
...
</programlisting>
	    </example>
	</section>

	<section id="app_lua.f.lua_runstring">
	    <title>
		<function moreinfo="none">lua_runstring(script)</function>
	    </title>
	    <para>
		Execute the Lua script stored in parameter. The parameter can be
		a string with pseudo-variables. The script is executed in Lua context
		specific to loaded Lua files at startup.
	    </para>
		<example>
		<title><function>lua_runstring</function> usage</title>
		<programlisting format="linespecific">
...
if(!lua_runstring("KSR.log([[err]], [[----------- Hello World from $fU\n]])"))
{
    xdbg("SCRIPT: failed to execute lua script!\n");
}
...
</programlisting>
	    </example>
	</section>

    </section>

    <section>
        <title>RPC Commands</title>
        <section id="app_lua.r.list">
            <title>
            <function moreinfo="none">app_lua.list</function>
            </title>
            <para>
            Lists the id and path for every script loaded by
            the load parameter.
            </para>
            <para>
            Name: <emphasis>app_lua.list</emphasis>
            </para>
            <para>Parameters: <emphasis>none</emphasis></para>
            <para>
            Example:
            </para>
            <programlisting  format="linespecific">
...
    &kamcmd; app_lua.list
...
            </programlisting>
        </section>
        <section id="app_lua.r.reload">
            <title>
            <function moreinfo="none">app_lua.reload</function>
            </title>
            <para>
            Marks the need to reload the selected script.
            The actual reload is done by every working process when the next
            call to lua_run function is executed.
            If no parameter is added all the scripts are selected to be reloaded.
            </para>
            <para>
            Name: <emphasis>app_lua.reload</emphasis>
            </para>
            <para>Parameters: <emphasis>id</emphasis></para>
            <para>
            Example:
            </para>
			<programlisting  format="linespecific">
...
    &kamcmd; app_lua.reload 0
...
            </programlisting>
        </section>
       <section id="app_lua.r.api_list">
            <title>
            <function moreinfo="none">app_lua.api_list</function>
            </title>
            <para>
			Lists the exported KEMI functions that can be used inside Lua
			scripts.
            </para>
            <para>
            Name: <emphasis>app_lua.api_list</emphasis>
            </para>
            <para>Parameters: <emphasis>none</emphasis></para>
            <para>
            Example:
            </para>
            <programlisting  format="linespecific">
...
    &kamcmd; app_lua.api_list
...
            </programlisting>
        </section>
    </section>

    <section>
	<title>Example of usage</title>
    <para>
		Create your Lua script and stored on file system,
		say: '/usr/local/etc/kamailio/lua/myscript.lua'.
    </para>
<programlisting format="linespecific">
...
function sr_append_fu_to_reply()
	KSR.hdr.append_to_reply("P-From: " .. KSR.pv.get("$fu") .. "\r\n");
end
...
</programlisting>
    <para>
		Load the script via parameter 'load' and execute function
		via lua_run(...).
    </para>
<programlisting format="linespecific">
...
modparam("app_lua", "load", "/usr/local/etc/kamailio/lua/myscript.lua")
...
route {
    ...
    if(!lua_run("sr_append_fu_to_reply"))
    {
        xdbg("SCRIPT: failed to execute lua function!\n");
    }
    ...
}
...
</programlisting>
    </section>
</chapter>

