This assumes you have installed OpenResty on a Linux system.

Let's say you have a module named core.lua that contains the following.

local _foo = {}

function _foo.hello() print("Hello") end
function _foo.world() print("World") end

return _foo

The resty command can be used to invoke the core.lua module. If the core.lua module is in your present working directory, here is how you would invoke the "hello" function.

~]# resty -e 'require "core".hello()'
Hello

Or the "world" function.

~]# resty -e 'require "core".world()'
World

If core.lua is not in your present working directory, the -I option can be used to point to the directory that contains core.lua.

~]# resty -I /usr/local/share/lua -e 'require "core".hello()'
Hello