The problem

Oftentimes happen we have to call an interactive program (ie: a program made to be used from a real user) from a batch script or from another non-interactive program.

The solution

In Linux we have several ways of doing this. Suppose we have the following script:

#!/bin/bash
# interactive-script.sh
read val
echo $val
 
read val
echo $val
 
read val
echo $val

we can call it in a non-interactively way using one of the following methods:

1. Input Pipe

   echo "yes
   no
   maybe" | interactive-script.sh
   

2. Redirect from File

   interactive-script.sh < answers.txt
   

3. Heredocs

   interactive-script.sh << ANSWERS
   yes
   no
   maybe
   ANSWERS
   

4. Herestring

   interactive-script.sh <<< $'yes\nno\nmaybe\n'