Make use of the possibility to return a string from Lua in order to implement *out functionality

plugins/lua/lua_action.c

@@ -7,19 +7,27 @@ CLISH_PLUGIN_SYM(clish_plugin_lua_action)
 	clish_context_t *context = (clish_context_t *) clish_context;
 	lua_State *L = clish_shell__get_udata(context->shell, LUA_UDATA);
 
-	int res = 0, result = -1;
+	int res = 0, result = -1, retnum = 0;
 
 	if (!script) /* Nothing to do */
 		return (0);
 
-	if (out)
-		*out = NULL; /* Does not work for now */
+	if (out) {
+		*out = NULL;
+		retnum = 1;
+	}
+
 
 	if ((res = luaL_loadstring(L, script))) {
 		l_print_error(L, __func__, "load", res);
-	} else if ((res = lua_pcall(L, 0, 0, 0))) {
+	} else if ((res = lua_pcall(L, 0, retnum, 0))) {
 		l_print_error(L, __func__, "exec", res);
 	} else {
+		if (retnum) {
+			if (lua_isstring(L, -1))
+				*out = lub_string_dup(lua_tostring(L, -1));
+			lua_pop(L, 1);
+		}
 		result = 0;
 	}