How do I answer install prompts (other than with "yes") automatically?

Question

Synopsis

I'm trying to build a Docker image, but it fails because one of the packages I'm trying to get with apt install prompts the user during the install process. I would like to reply to this prompt, but I can't figure out how to do it non-interactively.

Description

I'm building a Docker image, and my Dockerfile has the following line:

RUN apt install -y texlive-latex-extra

(This package has some LaTeX libraries that I need.)

During installation, this halts with:

Setting up tzdata (2018d-1) ...
debconf: unable to initialize frontend: Dialog
debconf: (TERM is not set, so the dialog frontend is not usable.)
debconf: falling back to frontend: Readline
Configuring tzdata
------------------

Please select the geographic area in which you live. Subsequent configuration
questions will narrow this down by presenting a list of cities, representing
the time zones in which they are located.

  1. Africa        6. Asia            11. System V timezones
  2. America       7. Atlantic Ocean  12. US
  3. Antarctica    8. Europe          13. None of the above
  4. Australia     9. Indian Ocean
  5. Arctic Ocean  10. Pacific Ocean
Geographic area:

At this point, it is waiting for some input. (There's another prompt after this for selecting timezone—I assume this is important to know for the \today directive in LaTeX files. ¯\_(ツ)_/¯)

How can I answer this non-interactively?

What I've tried so far

I've tried doing this:

apt install -y texlive-latex-extra <(echo 12 && echo 2)

and this:

echo 12 && echo 2 | apt install -y texlive-latex-extra

The first one died with this error:

apt install -y texlive-latex-extra <(echo 12 && echo 9)

and the second one seemed to have no effect.

For reference, here is my Dockerfile up until this point:

FROM ubuntu:latest

RUN apt update && apt upgrade -y && apt install -y curl bzip2 tar make gcc wget gnupg unzip
RUN apt install -y texlive
RUN apt install -y nodejs npm git
RUN npm install -g bower
RUN apt install -y texlive-latex-extra

UPDATE

I found something close here which suggested running apt install with DEBIAN_FRONTEND=noninteractive. This solved my problem sufficiently. :) However, I still would like to know how to respond to prompts, as the solution offered there only offered how to suppress them.

Answer 1

If you want to script a terminal interaction, you could use expect on Linux (that might not be very easy; you need to predict the interactions).

Remember that terminal emulators are complex and arcane things (because terminals like VT100 have been complex). See termios(3), pty(7) and read The Tty demystified.