Making a loop function to open a door.

So im new to LUA, I know the basics of java. I was trying to make a program that, when run, would check if a redstone output was true, and if it was true set it to false, if it was false set it to true. But im not sure exactly how to check its original state, here is what i have so far.

Spoiler

if
redstone.setOutput("back", true)
then
redstone.setOutput("back", true) == redstone.setOutput("back", false)
else
redstone.setOutput("back", false) == redstone.setOutput("back", true)
end

I tried making line 2 say "redstone.Output("back", true)" but I had no sucess.

So the question is, how do i make this work?

You can use this:

 if rs.getOutput("back") then rs.setOutput("back",false) else rs.setOutput("back",true) end 

It checks if it's already outputting a signal, then if so, it shuts it off. You can learn more about the Redstone API by clicking on the link.

OH getOutput, thats where i was having issues. Thanks :D/>/>

Also, rs.setOutput("back", not rs.getOutput("back")) would always toggle the output.