The Auxiliary Library
The auxiliary library provides several convenient functions to interface C with Lua. While the basic API provides the primitive functions for all interactions between C and Lua, the auxiliary library provides higher-level functions for some common tasks.
All functions from the auxiliary library are defined in header file lauxlib.h and have a prefix luaL_.
All functions in the auxiliary library are built on top of the basic API, and so they provide nothing that cannot be done with this API.
Several functions in the auxiliary library are used to check C function arguments. Their names are always luaL_check* or luaL_opt*. All of these functions raise an error if the check is not satisfied. Because the error message is formatted for arguments (e.g., "=bad argument #1="), you should not use these functions for other stack values.