Mastering the Nmap Scripting Engine

Flow control structures

Some classic control structures are implemented in Lua, such as the if-then conditional statements, a few different loop types, and the break and continue functions. Let's review these structures briefly. The objective of the following sections is to get you familiar with the syntax used in this language.

Conditional statements – if-then, else, and elseif

The if-then conditional statement evaluates an expression and executes a block of code if the expression is true. It uses the following syntax:

if status.body then
  --Do something
end

Lua also supports an else-if conditional statement with the elseif keyword:

if status.code == 200 then
  --Do something
elseif status.code == 301 then
  --Do something else
end

An else statement does ...