How to generate requirements.txt file from existing Pipfile.lock without locking?
When I run pipenv lock -r it ignores existing Pipfile.lock and does locking process again.

There is a workaround for this:

$ pipenv sync
$ pipenv run pip freeze

In my particular situation I'm building docker image and using requirements.txt in Dockerfile. I'd like to avoid creating virtual environment on the host machine just to be able to create requirements.txt.