Lua Programming Language

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Compiling Lua source files

Let’s say you have a lua program – hello.lua.

print("Hello Lua!")

The source code can be compiled into a binary file using luac

$ luac -o hello.luac hello.lua

The file hello.luac can then be used in place of the source file. Using the binary file has some advantages like: faster loading, simple source hiding etc.,

To run a .luac file (this is my own convention, the Lua docs do not seem to prefer any particular suffix for the compiled file), you still need to call the lua interpreter,

$ lua hello.luac

Creating standalone executables for lua

A Lua source file can be converted into a executable using different methods. srlua appears to be the popular one.

Download srlua from here and build it using make. Copy glue and srlua files into a convenient location, say ~/bin.

You can now create standalone executable from the Lua source file –hello.lua thus:

$ ~/bin/glue ~/bin/srlua hello.lua hello
$ chmod +x hello
$ ./hello
Hello Lua!

Installing new software packages

Luarocks is the deployment and package management system for Lua. Think CPAN for Perl and PyPI for Python.

I have installed Lua in my $HOME directory. That is, lua interpreter resides in $HOME/bin, include files in $HOME/include etc.,

So, to install Luarocks:

$ export PREFIX=$HOME
$ ./configure --prefix=$PREFIX --sysconfdir=$PREFIX/luarocks --force-config

Installing new lua packages is as simple as:

$ cd 
luarocks install luasocket

where luasocket is a new package that is fetched from the luarocks mirrors and installed.

To make this package available to the Lua interpreter export LUA_PATH thusly:

export LUA_PATH="/opt/local/share/lua/5.1//?.lua;/opt/local/lib/luarocks/?.lua;;"

Also, to explicitly add paths to a script:

# cat t_paths.lua
package.path = package.path.. ";/opt/local/share/lua/5.1/?.lua"
package.cpath = package.cpath.. ";/opt/local/lib/lua/5.1/?.so"
local s = require "socket"
print(s._VERSION)

Incidentally, on the day I was learning aobut luarocks, luaforge.net, the main lua modules repository was down. Friendly folks on the #lua IRC channel told me to add mirrors to the luarocks configuration.

$ vim ~/luarocks/config.lua

I replaced the luaforge.net line with "http://www.luarocks.org/repositories/rocks/",.

Misc. Notes

Setting up LUA_PATH and LUA_CPATH is always more complicated than it needs to be. Remember not to have any spaces after the path seperator ;.

LuaDist appears promising to set up virtualenv like sandboxed environments (and more..) for lua.