example C extension for Lua

lsleep.c

#include <unistd.h>

#include <lua.h>
#include <lauxlib.h>

static int lua_sleep(lua_State *L) {
    int ms = luaL_checkinteger(L, 1);
    usleep(ms * 1000);
    return 0;
}

int luaopen_lsleep(lua_State *L) {
    static const luaL_Reg lsleep[] = {
        { "sleep", lua_sleep },
        { NULL, NULL }
    };

    lua_newtable(L);
#if LUA_VERSION_NUM > 501  // lua 5.2
    luaL_setfuncs(L, lsleep, 0);
#else                      // lua 5.1
    luaL_register(L, NULL, lsleep);
#endif
    return 1;
}

Makefile

PC      = pkg-config
LUA     = lua5.1
CFLAGS  = `$(PC) --cflags $(LUA)` -Wall -fPIC
LDFLAGS = `$(PC) --libs $(LUA)`

lsleep.so: lsleep.c
	gcc -shared $(CFLAGS) $(LDFLAGS) -o $@ $^

clean:
	-rm lsleep.so

sleep.lua

local s = require "lsleep"
s.sleep(1000)