Bash shells communication

Hello all,
I have the following problem. In a Bash shell I run a program (I don't have the source code) which will execute some steps. At every step the program will wait for a user input. So I would like that another script which is running on a different shell will send these input togheter with the "enter button pression". In a such way the software which is running on the first shell will advance according to the script.

Some ideas?
Thanks in advance.

use 'expect'

Expect - Expect - Home Page

What is this?

If you have the input in file you can try something like:

program < inputfile

Ok I will try.
Thanks.