Input from within shell script

Question

I have a script that calls an application that requires user input, e.g. run app that requires user to type in 'Y' or 'N'.
How can I get the shell script not to ask the user for the input but rather use the value from a predefined variable in the script?

In my case there will be two questions that require input.

Answer 1

You can pipe in whatever text you'd like on stdin and it will be just the same as having the user type it themselves. For example to simulating typing "Y" just use:

echo "Y" | myapp

or using a shell variable:

echo $ANSWER | myapp

There is also a unix command called "yes" that outputs a continuous stream of "y" for apps that ask lots of questions that you just want to answer in the affirmative.