Export an org-mode file as a PDF via command line?

Question

What command-line arguments do I use to get Emacs to export an org-mode file to a Beamer PDF? (I want to create a Makefile that produces a PDF when the user runs make.)

I tried following this answer but couldn't get it to work:

$ emacs --batch foo.org -f org-beamer-export-to-pdf
Symbol's function definition is void: org-beamer-export-to-pdf
$ emacs --batch -l ox-beamer foo.org -f org-beamer-export-to-pdf
Cannot open load file: ox-beamer

The above error comes from the fact that the org-mode files are in a custom location and my ~/.emacs.d/init.el is not loaded (--batch implies -q a.k.a. --no-init-file).

If I tell Emacs to load my init file it will work:

$ emacs --batch -l ~/.emacs.d/init.el foo.org -f org-beamer-export-to-pdf

However, this doesn't work for other users that use ~/.emacs or ~/.emacs.el instead of ~/.emacs.d/init.el. I tried telling Emacs to load user-init-file but it didn't work:

$ emacs --batch --eval '(load user-init-file)' foo.org -f org-beamer-export-to-pdf
Wrong type argument: stringp, nil

Assuming all users can successfully press C-x C-e l P to export a Beamer PDF when using Emacs interactively, what non-interactive command will produce a PDF?

Answer 1

The following worked for me:

emacs \
    -u "$(id -un)" \
    --batch \
    --eval '(load user-init-file)' \
    foo.org \
    -f org-beamer-export-to-pdf

Thanks go to @mutbuerger for the hint to pass -u <username> to get user-init-file defined.

Answer 2

I'm using self-compiled emacs 27.0.9x on Linux and macOS. To generate my presentations, I use org-mode.

emacs -Q \
  --batch "(require 'ox-beamer)" \
  <input>.org -f org-beamer-export-to-pdf

works for me.