kumomta/docs/tutorial/subs/lua_resources.md

Lua Resources

Lua is portugese for moon. It is also the name of the scripting language we use in KumoMTA. Because it is a name, Lua is always capitalized.

Understanding Lua is not required to deploy and use KumoMTA, but it will help you leverage the full power of this incredibly flexible system. Lua is easy to learn, easy to read, and easy to implement.

You can find many resources at the [official Lua site including online documentation and physical reference books.

Here is a very (very) simplified primer to help you read the KumoMTA script/configs.

Simplified Lua Cheat Sheet

-- A single line comment in Lua is 2 dashes (--)

--[[ A multi line comment in Lua
     is framed in 2 dashes and 2 square brackets
   ]]
--

Variables should always be declared as "local" unless you fully understand the affects of setting a global variable.  [Global variables are dangerous](http://wiki.c2.com/?GlobalVariablesAreBad).

local myvar
local myvar = 32

Global variables are implied by excluding the word "local".

myvar = 32 -- this is a GLOBAL variable

Lua supports the following relational operators:

Symbol	Meaning
==	equality
~=	inequality
<	less than
>	greater than
<=	less than or equal to
>=	greater than or equal to

You can concatenate strings with two dots surrounded by spaces.

print('This' .. ' is ' .. 'true.')

Functions, conditionals, and loops always end with "end"

if x == 2 then
  y = 6
end

function dostuff(things)
  print(things)
end