Lua: run code while waiting for input

I'm currently working on a lua program. I want to use it in Minecraft with a mod called "OpenComputers" which allows the use of lua scripts on emulated systems. The programm I'm working on is relatively simple: you have a console and you enter a command to control a machine. It looks like this:

while(true) do
  io.write("Enter command\n>")
  cmd = io.read()
  -- running code to process the command
end

But the problem is: I need a routine running in the background which checks data given by the machine.

while(true) do
  -- checking and reacting
end

How can I make this work?

• I can't jump to a coroutine while waiting on io.read()
• It's not enough to check after someone used a command (sometimes I don't use it for days but I still have to keep an eye on it)

I'm relatively new to lua so please try to give a simple solution and - if possible - one that does not rely on third party tools.

Thank you :)

If you have some experience with opencomputers, you can add a(n asynchronous) listener for "key_down", and store the user input in a string (or whatever you want).

For example:

local userstr = ""
function keyPressed(event_name, player_uuid, ascii)
    local c = string.char(ascii)
    if c=='\n' then
        print(userstr)
        userstr = ""
    else
        userstr=userstr..c
    end
    --stores keys typed by user and prints them as a string when you press enter
end

event.register("key_down", keyPressed)