Passing arguments to an interactive program non-interactively

Question

Many ways

pipe your input

echo "yes
no
maybe" | your_program

redirect from a file

your_program < answers.txt

use a here document (this can be very readable)

your_program << ANSWERS
yes
no
maybe
ANSWERS

use a here string

your_program <<< $'yes\nno\nmaybe\n'

For more complex tasks there is expect ( http://en.wikipedia.org/wiki/Expect ). It basically simulates a user, you can code a script how to react to specific program outputs and related stuff.

This also works in cases like ssh that prohibits piping passwords to it.

You can put the data in a file and re-direct it like this:

$ cat file.sh
#!/bin/bash

read x
read y
echo $x
echo $y

Data for the script:

$ cat data.txt
2
3

Executing the script:

$ file.sh < data.txt
2
3

Just want to add one more way. Found it elsewhere, and is quite simple. Say I want to pass yes for all the prompts at command line for a command "execute_command", Then I would simply pipe yes to it.

yes | execute_command

This will use yes as the answer to all yes/no prompts.

You can also use printf to pipe the input to your script.

var=val
printf "yes\nno\nmaybe\n$var\n" | ./your_script.sh