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copied!<p>The likely problem is that <a href="http://www.lua.org/manual/5.1/manual.html#luaL_loadfile" rel="nofollow noreferrer"><code>luaL_loadfile()</code></a> is documented to return the same values as <a href="http://www.lua.org/manual/5.1/manual.html#lua_load" rel="nofollow noreferrer"><code>lua_load()</code></a> or one additional error code. In either case, the return value is an <code>int</code> where 0 means success and a nonzero value is an error code.</p> <p>So, the test <code>luaL_loadfile(...) == NULL</code> is <strong>true</strong> if the file was loaded, but the code calls that an error and returns.</p> <p>The function <code>lua_pcall()</code> also returns a status code, and you may want to verify that as well. </p> <p>Otherwise, the script as shown does create a global variable, and <code>lua_getglobal()</code> would retrieve that to the stack where it could be tested with <code>lua_isstring()</code>, or probably more usefully let you return its value if it is sufficiently string-like with <a href="http://www.lua.org/manual/5.1/manual.html#lua_tostring" rel="nofollow noreferrer"><code>lua_tostring()</code></a>. The latter function will return either a <code>const char *</code> pointing at a nul-terminated string, or NULL if the value at the stack index can't be converted to a string. See the Lua reference manual as linked for the rest of the details and a caveat about using <code>lua_tostring()</code> inside a loop.</p> <p><strong>Edit:</strong> I added better links to the manual in a couple of places.</p>

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