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4 – The Application Program Interface

This section describes the C API for Lua, that is, the set of C functions available to the host program to communicate with Lua. All API functions and related types and constants are declared in the header file lua.h.

Even when we use the term "function", any facility in the API may be provided as a macro instead. Except where stated otherwise, all such macros use each of their arguments exactly once (except for the first argument, which is always a Lua state), and so do not generate any hidden side-effects.

As in most C libraries, the Lua API functions do not check their arguments for validity or consistency. However, you can change this behavior by compiling Lua with the macro LUA_USE_APICHECK defined.

The Lua library is fully reentrant: it has no global variables. It keeps all information it needs in a dynamic structure, called the Lua state.

Each Lua state has one or more threads, which correspond to independent, cooperative lines of execution. The type lua_State (despite its name) refers to a thread. (Indirectly, through the thread, it also refers to the Lua state associated to the thread.)

A pointer to a thread must be passed as the first argument to every function in the library, except to lua_newstate, which creates a Lua state from scratch and returns a pointer to the main thread in the new state.

lua_isnumber
  • References/Lua/Lua/API/Functions and Types

lua_isnumber[-0, +0, –] int lua_isnumber (lua_State *L, int index); Returns 1 if the value at the given

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lua_pushboolean
  • References/Lua/Lua/API/Functions and Types

lua_pushboolean[-0, +1, –] void lua_pushboolean (lua_State *L, int b); Pushes a boolean value with value

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lua_len
  • References/Lua/Lua/API/Functions and Types

lua_len[-0, +1, e] void lua_len (lua_State *L, int index); Returns the length of the value at

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lua_rawgetp
  • References/Lua/Lua/API/Functions and Types

lua_rawgetp[-0, +1, –] int lua_rawgetp (lua_State *L, int index, const void *p); Pushes onto the stack

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lua_yieldk
  • References/Lua/Lua/API/Functions and Types

lua_yieldk[-?, +?, e] int lua_yieldk (lua_State *L, int nresults, lua_KContext

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lua_getextraspace
  • References/Lua/Lua/API/Functions and Types

lua_getextraspace[-0, +0, –] void *lua_getextraspace (lua_State *L); Returns a pointer to a raw memory

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lua_pushcfunction
  • References/Lua/Lua/API/Functions and Types

lua_pushcfunction[-0, +1, –] void lua_pushcfunction (lua_State *L, lua_CFunction f); Pushes a C function

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lua_resume
  • References/Lua/Lua/API/Functions and Types

lua_resume[-?, +?, –] int lua_resume (lua_State *L, lua_State *from, int nargs); Starts and resumes a coroutine

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lua_pushfstring
  • References/Lua/Lua/API/Functions and Types

lua_pushfstring[-0, +1, e] const char *lua_pushfstring (lua_State *L, const char *fmt, ...); Pushes

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lua_typename
  • References/Lua/Lua/API/Functions and Types

lua_typename[-0, +0, –] const char *lua_typename (lua_State *L, int tp); Returns the name of the type encoded

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