Get Lua string from C -

i'm trying learn lua , how interface , c it. first attempt follows has been simplified include issue i'm seeing.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <linux/limits.h> /* path_max */ #include <unistd.h> #include <getopt.h> #include <lua.h> #include <lualib.h> #include <lauxlib.h>  #define exitf exit(exit_failure)  lua_state* lua;  void stackdump(lua_state* lua) {     int i, t;     int top = lua_gettop(lua);      (i = 1; <= top; i++)     {         t = lua_type(lua, i);          switch (t)         {             case lua_tstring:                 printf("\"%s\"", lua_tostring(lua, i));                 break;              case lua_tboolean:                 printf(lua_toboolean(lua, i) ? "true" : "false");              case lua_tnumber:                 printf("%g", lua_tonumber(lua, i));                 break;              default:                 printf("%s", lua_typename(lua, t));                 break;         }          if (i < top)            printf(", ");     }      printf("\n"); }  int main(int argc, char** argv) {     int opt;     char cfgfile[path_max];     cfgfile[0] = 0;      lua = lual_newstate();     lual_openlibs(lua);      stackdump(lua);      while ((opt = getopt(argc, argv, "c:")) != -1)     {         switch (opt)         {             case 'c':                 strncpy(cfgfile, optarg, path_max);                 cfgfile[path_max - 1] = 0;                 break;         }     }      if (cfgfile[0] == 0)     {         fprintf(stderr, "no cfg file specified\n");         return exit_failure;     }      printf("cfgfile = \"%s\"\n", cfgfile);      if (lual_loadfile(lua, cfgfile) != lua_ok)     {         fprintf(stderr, "%s\n", lua_tostring(lua, -1));         lua_pop(lua, 1);         lua_close(lua);         return exit_failure;     }      stackdump(lua);      lua_getglobal(lua, "program");      stackdump(lua);      if (lua_isstring(lua, -1) == 0)     {         fprintf(stderr, "`program` should string\n");         lua_close(lua);         return exit_failure;     }      char execarg0[256];      strncpy(execarg0, lua_tostring(lua, -1), 256);     lua_pop(lua, 1);      lua_close(lua);      return exit_success; } 

lua script:

#!/usr/bin/env lua  program = "echo" 

what i'm seeing when running is:

$ ./wrapper2 -c wrapper2.lua  cfgfile = "wrapper2.lua" function function, nil `program` should string 

note empty line intentional; stackdump() tells stack empty @ point. seems call lua_getglobal(lua, "program") pushing nil on stack instead of string "echo". please me work out why i'm seeing this?

as side question: why there function pushed on stack (presumably lual_loadfile())? don't remember reading functions pushed on stack automatically.

lual_loadfile loads lua script not execute , not define global program. use lual_dofile instead.

lual_loadfile compiles lua script , leaves code lua function on stack.

lual_dofile calls lual_loadfile , calls function.

see manual entries lual_loadfile , lual_dofile.