Scripting Help - Check for String in File

[JungleKitty]

I need to check for a sting in my hosts file and write a new line if its not present. I am completely new to Lua.
Here is my non working script: see image

Im hoping for an example demonstrating a task similar to mine.

[JungleKitty]

UPDATED BUT STILL NOT FUNTIONING: different string but same concept

[JungleKitty]

solution!