Run linux program from shell script with multi-line input

Question

I want to run a specific program from a script which normally aks the user for some input (several times).

For example, when I start the program in the shell and my input would be:

t [ENTER]
3 [ENTER]
12 [ENTER]
e [ENTER]

where one has to wait after every line that the program wants the next input.

I guess there is a solution like

echo t | prog
echo 3 | prog
echo 12 | prog
echo e | prog

but after the first line the program runs with no input because of an empty buffer. How can I fix that?

Answer 1

Prime use case for a here-document:

prog <<EOF
t
3
12
e
EOF

Answer 2

Guess it depends on what kind of shell you are using. With bash you can echo multiple lines like,

$ echo "t
> 3
> 12
> e" | prog

Answer 3

The read command reads a single line, terminated by a newline. You can include newlines in your echo:

echo "t\\n3\\n12\\ne" | prog