lua通過一個運行時棧來維護參數傳遞及返回，使用lua_to*等函數獲取lua傳遞到C函數的參數，使用lua_push*從C函數返回值到lua腳本。此外也可以使用lua_getglobal從C函數獲取lua腳本定義的全局變量。
#include <lua.h>
#include <lauxlib.h>
#include <stdlib.h> /* For function exit() */
#include <stdio.h> /* For input/output */
void bail(lua_State *L, char *msg){
fprintf(stderr, "\nFATAL ERROR:\n %s: %s\n\n",
msg, lua_tostring(L, -1));
exit(1);
}
int lua_func_from_c(lua_State *L)
{
printf("This is C\n");
int argc = lua_gettop(L); /* number of arguments */
const char * str = lua_tostring(L,1); /* the first argument: string */
int num = lua_tonumber(L,2); /* the second argument: number */
printf("The first argument: %s\n", str);
printf("The second argument: %d\n", num);
lua_getglobal(L,"global_var");
const char * global_str = lua_tostring(L,-1);
printf("global_var is %s\n", global_str);
int the_second_ret = 2*num;
lua_pushstring(L, "the first return");
lua_pushnumber(L, the_second_ret);
return 2; /* tell lua how many variables are returned */
}
int main(int argc, const char *argv[])
{
if(argc != 2)
{
return 1;
}
lua_State *L = luaL_newstate(); /* Create new lua state variable */
/* Load Lua libraries, otherwise, the lua function in *.lua will be nil */
luaL_openlibs(L);
/* register new lua function in C */
lua_register(L, "lua_func_from_c", lua_func_from_c);
if( luaL_loadfile(L,argv[1]) ) /* Only load the lua script file */
bail(L, "luaL_loadfile() failed");
if( lua_pcall(L,0,0,0) ) /* Run the loaded lua file */
bail(L, "lua_pcall() failed");
lua_close(L); /* Close the lua state variable */
return 0;
}
lua腳本（my.lua）如下所示(在lua腳本中，如果變量不用local明確聲明爲局部變量，則默認爲全局變量)：
print("Hello world")
global_var = "this is a global string"
first, second = lua_func_from_c("the first one", 2)
print("the first returned", first)
print("the second returned", second)
執行結果：
Hello world
This is C
The first argument: the first one
The second argument: 2
global_var is this is a global string
the first returned the first return
the second returned 4