How to redirect the Lua 'print' function in C/C++ to your own C/C++ function

redirectPrint.cpp

#include<iostream>

#include'lua.hpp'

//extern 'C' {

//#include 'lua.h'

//#include 'lualib.h'

//#include 'lauxlib.h'

//}

staticintl_my_print(lua_State* L) {

int nargs = lua_gettop(L);

std::cout << 'in my_print:';

for (int i=1; i <= nargs; ++i) {

std::cout << lua_tostring(L, i);

}

std::cout << std::endl;

return0;

}

staticconststructluaL_Reg printlib [] = {

{'print', l_my_print},

{NULL, NULL} /* end of array */

};

intmain(void) {

lua_State* L = luaL_newstate();

luaL_openlibs(L);

lua_getglobal(L, '_G');

luaL_setfuncs(L, printlib, 0);

Lua_pop(L, 1);

luaL_dostring(L, 'print('Hello from Lua')');

lua_close(L);

return0;

}

In the second kind, Lua has the control and C is the library. Here, the C code is called library code. Both application code and library code use the same API to communicate with Lua, the so called C API. The C API is the set of functions that allow C code to interact with Lua. It comprises functions to read and write Lua global variables, to call Lua functions, to run pieces of Lua code, to register C functions so that. Lua is an open source language built on top of C programming language. Lua has its value across multiple platforms ranging from large server systems to small mobile applications. This tutorial covers various topics ranging from the basics of Lua to its scope in various applications.

commented Sep 7, 2017

commented Sep 15, 2017

If you don't have lua.hpp, remove that line and uncomment the imports right below it. If you are using a c compiler (not c++) then you can also remove the extern c declarations.

commented Oct 11, 2018

luaL_register(L, NULL, printlib); // for Lua versions < 5.2
luaL_setfuncs(L, printlib, 0); // for Lua versions 5.2 or greater

commented Apr 12, 2021

Dose not work exactly like the real print because using real print like print(io.read) will return it's id this one just causes a segmentation fault

In this article, we’ll cover the basics of the Lua programming language, including:

Let’s get started.

What is Lua?

Lua is a robust, lightweight, and embeddable scripting language that supports multiple programming methods, including procedural, object-oriented, functional, and data-driven programming.

As the primary focus on Lua is for scripting, it is rarely used as a standalone programming language. Instead, it is used as a scripting language that can be integrated (embedded) into other programs written in mainly C and C++. It also supports other programming languages via third-party plugins (NLua/KeraLua for .NET/C#).

Popular use cases for Lua include:

As a popular component in video game and game engine development. For example, Warframe, World of Warcraft, and CRYENGINE all use Lua.
As a programming language in many network programs, like CISCO Systems, Nmap, and ModSecurity.
As a programming language in industrial programs such as Adobe Lightroom and MySQL Workbench.
As a library that developers can integrate with their programs to enable scripting functionality.

Lua Call C Function

Being a scripting language, Lua does not have its own main application. Instead, it acts exclusively as an embedded part of the host application.

(Explore the most popular programming languages.)

How Lua works

There are two main components of Lua:

The Lua interpreter
The Lua virtual machine (VM)

Lua is not directly interpreted through a Lua file like other languages such as Python. Instead, it uses the Lua interpreter to compile a Lua file to bytecode. The Lua interpreter is written in ANSI C, making it highly portable and capable of running on a multitude of devices.

Usually, the compilation is done at the runtime. However, sometimes it can be done before the runtime to increase load times. Then the Lua virtual machine will run this compiled bytecode. The register-based architecture of the Lua virtual machine closely resembles actual hardware architectures, and it will increase the overall performance of the program.

Key features of Lua

So, what’s so great about Lua? These are the defining features:

Speed

Lua is considered one of the fastest programming languages among interpreted scripting languages. Como hackear clash of clans 2015. In particular, Lua can perform large task orders faster than most other programming languages in both benchmarking and real-world scenarios.

For more speed, an independent implementation of Lua called LuaJIT uses a just-in-time compiler that makes Lua even faster.

Size

Lua has a considerably smaller footprint than other programming languages, with its complete source code and documentation taking a mere 1.3 MB. The Lua interpreter with all the standard libraries takes 278K, while the complete Lua library takes only 466K.

This small size is ideal when integrating Lua into multiple platforms, from embedded devices to massive game engines, where every byte is valuable.

Portability & embeddability

With its small size, the portability of Lua is nearly unlimited; any platform that supports the standard C compiler can run Lua out of the box. Lua’s speed and size become huge advantages when embedding Lua with another programming language. That’s because they can help increase the speed of the program without hindering any existing functionality.

Importantly, Lua does not require complex rewrites to be compatible with other programming languages. Lua can be used with primary programming languages like C, C++, Java, C#, etc. and other scripting languages like Perl and Ruby, further extending its usability.

Simplicity

Lua is simple in design yet provides powerful functionality. One of the core features of Lua is meta-mechanisms which enable developers to implement features—rather than providing a bunch of features directly in the language itself.

Lua also comes with incremental garbage collection, reducing memory usage and implementation complexity. Its sandboxing feature can be used to isolate functions and resources. This increases the security of the program and provides coroutines for multitasking.

All these features come with a simple syntax and easily understandable format so that anyone can easily pick up Lua and use it in their programs.

License

Lua is free and open-source software distributed under the

How To Lua C