How can I call Lua scripts from a C program?

Question

I have 2 lua scripts. One require another one. So how can I call it from a C program?

For example:

main.lua

local foo = require "foo"

function main()
    foo.bar()
end

main()

foo.lua

function bar( )
    io.write("hello, world!\n")
end

And this is my C program:

#include <lauxlib.h>
#include <lua.h>
#include <lualib.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
    int status, result;
    lua_State *L;
    L = luaL_newstate();
    luaL_openlibs(L);

    status = luaL_loadfile(L, "main.lua");
    if (status) {
        fprintf(stderr, "Couldn't load file: %s\n", lua_tostring(L, -1));
        exit(1);
    }

    result = lua_pcall(L, 0, LUA_MULTRET, 0);
    if (result) {
        fprintf(stderr, "Failed to run script: %s\n", lua_tostring(L, -1));
        exit(1);
    }

    lua_close(L);

    return 0;
}

It throws a runtime error:

Failed to run script: main.lua:130: module 'foo' not found: no field package.preload['foo'] no file '/usr/local/share/lua/5.3/foo.lua' no file '/usr/local/share/lua/5.3/foo/init.lua' no file '/usr/local/lib/lua/5.3/foo.lua' no file '/usr/local/lib/lua/5.3/foo/init.lua' no file './foo.lua' no file './foo/init.lua' no file '/usr/local/lib/lua/5.3/foo.so' no file '/usr/local/lib/lua/5.3/loadall.so' no file './foo.so'

I think it is because foo.lua is not loaded into the lua virtual machine, but I can't find API like load files or do files. So what should I do?

BladeMight BladeMight · Accepted Answer · 2019-03-08T11:32:36

It works fine, your foo.lua is wrong, change it to:

local foo = {}

function foo.bar()
    io.write("Hello World!\n")
end

return foo

and it works:

$ ls
foo.lua  luabr.c  main.lua
BladeMight ~/lua/tests/605
$ gcc luabr.c -llua && ./a
Hello World!

** luabr.c is your C program code.

How can I call Lua scripts from a C program?

1 Answers