I work with Amazon Linux instances and I have a couple scripts to populate data and install all the programs I work with, but a couple of the programs ask:
D
The 'yes' command will echo 'y' (or whatever you ask it to) indefinitely. Use it as:
yes | command-that-asks-for-input
or, if a capital 'Y' is required:
yes Y | command-that-asks-for-input