What is an .env (or dotenv) file exactly?

Question

There's a lot of programs out there that can utilize .env files. Most of them support the basic bash-syntax, others support more advanced things like templating within the .env files. The way you're supposed to use .env files varies a lot as well. Often in this context, you'll year from the 12-factor-app which states that you should export (some) configuration as environment variables, that apparently lead to two use cases:

Some dotenv programs do just that: you prefix your command on the shell with dotenv and the variables in the dotenv file will magically be available in you process.
Others however provide libraries that actually read .env files from within your code -- a very different approach since your code is suddenly interpreting .env files directly and does not "see" the environment variables anymore.

Since there's so many different interpretations of usage, use-cases and syntax, is there a proper definition of .env files or some commonly accepted standard? If not, at least some historical references?

user_2142505 · Answer

It appears that .env files lack a complete definition.

This reference:

https://devcenter.heroku.com/articles/heroku-local

Links here:

http://blog.daviddollar.org/2011/05/06/introducing-foreman.html

Which leads here:

https://ddollar.github.io/foreman/

Which contains this:

ENVIRONMENT
    If a .env file exists in the current directory, the default
    environment will be read from it. This file should contain key/value
    pairs, separated by =, with one key/value pair per line.

        FOO=bar
        BAZ=qux

What is an .env (or dotenv) file exactly?

1 Answers