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Welcome to Lua 5.2

about · installation · changes · license · reference manual

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This is a work version of Lua 5.2. All details may change in the final version.

About Lua

Lua is a powerful, fast, lightweight, embeddable scripting language developed by a team at PUC-Rio, the Pontifical Catholic University of Rio de Janeiro in Brazil. Lua is free software used in many products and projects around the world.

Lua's official web site provides complete information about Lua, including an executive summary and updated documentation, especially the reference manual, which may differ slightly from the local copy distributed in this package.

Installing Lua

Lua is distributed in source form. You need to build it before using it. This should be straightforward because Lua is implemented in pure ANSI C, and compiles unmodified in all known platforms that have an ANSI C compiler. Lua also compiles unmodified as C++.

The instructions below are for Unix-like platforms. There are also instructions for other systems. See below for customization options.

Building Lua

In most Unix-like platforms, simply do "make" with a suitable target. Here are the details.

1. Open a terminal window and move to the top-level directory, which is named lua-5.2. The Makefile there controls both the build process and the installation process.

2. Do "make" and see if your platform is listed. The platforms currently supported are:

   aix ansi bsd freebsd generic linux macosx mingw posix solaris

   If your platform is listed, just do "make xxx", where xxx is your platform name.

   If your platform is not listed, try the closest one or posix, generic, ansi, in this order.

3. The compilation takes only a few moments and produces three files in the src directory: lua (the interpreter), luac (the compiler), and liblua.a (the library).

4. If you want to check that Lua has been built correctly, do "make test" after building Lua. This will run the interpreter on a "hello world" Lua program from the test directory. You may want to try other example programs in that directory.

Installing Lua

Once you have built Lua, you may want to install it in an official place in your system. In this case, do "make install". The official place and the way to install files are defined in Makefile. You'll probably need the right permissions to install files.

If you want to build and install Lua in one step, do "make xxx install", where xxx is your platform name.

If you want to install Lua locally, then do "make local". This will create a directory install with subdirectories bin, include, lib, man, and install Lua there as follows:

bin:

lua luac

include:

lua.h luaconf.h lualib.h lauxlib.h lua.hpp

lib:

liblua.a

man/man1:

lua.1 luac.1

These are the only directories you need for development.

There are man pages for lua and luac, in both nroff and html, and a reference manual in html in doc, some sample code in test, and some useful stuff in etc. You don't need these directories for development.

If you want to install Lua locally, but in some other directory, do "make install INSTALL_TOP=xxx", where xxx is your chosen directory.

Customization

Three kinds of things can be customized by editing a file:

• Where and how to install Lua — edit Makefile.
• How to build Lua — edit src/Makefile.
• Lua features — edit src/luaconf.h.

You don't actually need to edit the Makefiles because you may set the relevant variables in the command line when invoking make.

On the other hand, if you need to customize some Lua features, you'll need to edit src/luaconf.h before building and installing Lua. The edited file will be the one installed, and it will be used by any Lua clients that you build, to ensure consistency. (Further customization is possible by editing the Lua sources.)

We strongly recommend that you enable dynamic loading. This is done automatically for all platforms listed above that have this feature and also for Windows.

Building Lua on other systems

If you're not using the usual Unix tools, then the instructions for building Lua depend on the compiler you use. You'll need to create projects (or whatever your compiler uses) for building the library, the interpreter, and the compiler, as follows:

library:

lapi.c lcode.c lctype.c ldebug.c ldo.c ldump.c lfunc.c lgc.c llex.c lmem.c lobject.c lopcodes.c lparser.c lstate.c lstring.c ltable.c ltm.c lundump.c lvm.c lzio.c lauxlib.c lbaselib.c lbitlib.c ldblib.c liolib.c lmathlib.c loslib.c ltablib.c lstrlib.c loadlib.c linit.c

interpreter:

library, lua.c

compiler:

library, luac.c print.c

If you use Visual Studio .NET, you can use etc/luavs.bat in its "Command Prompt".

If all you want is to build the Lua interpreter, you may put all .c files in a single project, except for luac.c and print.c. Or just use etc/one.c.

To use Lua as a library in your own programs you'll need to know how to create and use libraries with your compiler. Moreover, to dynamically load C libraries for Lua you'll need to know how to create dynamic libraries and you'll need to make sure that the Lua API functions are accessible to those dynamic libraries — but you do not want to link the Lua library into each dynamic library. For Unix, we recommend that the Lua library be linked statically into the host program and its symbols exported for dynamic linking; src/Makefile does this for the Lua interpreter. For Windows, we recommend that the Lua library be a DLL.

As mentioned above, you may edit src/luaconf.h to customize some features before building Lua.

Changes since Lua 5.1

Here are the main changes in Lua since its last release. The reference manual lists the incompatibilities that had to be introduced.

Language

• new lexical environments.
• no more fenv for threads.
• ephemeron tables.
• yieldable pcall/metamethods.
• tables honor the __len metamethod.
• max constants per function raised to 2^26.
• hex escapes in strings.
• no more verification of opcode consistency.

Libraries

• new library for bitwise operations.
• new metamethods __pairs and __ipairs.
• arguments for function called through xpcall.
• optional argument to load (to control binary x text).
• loadlib may load libraries with global names (RTLD_GLOBAL).
• new function package.searchpath.
• optional base in math.log.
• file:write returns file.
• closing a pipe returns exit status.
• os.exit may close state.
• new option 'isrunning' for collectgarbage and lua_gc.
• frontier patterns.
• ipairs now goes until #t.

Implementation

• emergency garbage collector (core forces a full collection when allocation fails).
• ephemeron tables (tables with weak keys only visit value when key is accessible)
• handling of non-string error messages in the standalone interpreter.
• udata with finalizers are kept in a separated list for the GC.
• CallInfo stack now is a linked list.
• internal (immutable) version of ctypes.
• parser uses much less C-stack space (no more auto arrays).
• new hash for floats.

License

Lua is free software licensed under the terms of the MIT license reproduced below, and can be used for any purpose, including commercial purposes, at absolutely no cost without having to ask us. The only requirement is that if you do use Lua, then you should give us credit by including the appropriate copyright notice somewhere in your product or its documentation. For details and rationale, see this.

Copyright © 1994–2010 Lua.org, PUC-Rio.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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Last update: Wed Jan 13 15:35:05 BRST 2010