dot-env.el makes it easy to keep track of emacs configuration variables across multiple environments and machines. It aims to reproduce the functionality found in https://github.com/motdotla/dotenv, allowing you to specify values for config items that are likely to change across machines.

Examples of such config items are font sizes, paths to executables such as `ispell`, and authentication tokens.

(use-package dot-env
  :ensure t
  :config
  (dot-env-config))

dot-env.el implements 3 of the 4 public methods available in the original dotenv.js, skipping the decrypt() function in favor of GPG.

(dot-env-config (&optional path))
;; Load the values from file located at PATH and return them or an error.
;; PATH defaults to `user-emacs-directory'/.env.

(dot-env-parse (dotenv-str))
;; Parse DOTENV-STR into an association list and return the result.

(dot-env-populate (alist &optional override debug))
;; Load the values from the association list ALIST into `dot-env-environment'.
;; If OVERRIDE is non-nil, override existing values.
;; If debug is non-nil, print log messages.
;; ALIST should be in the form of '((symbol string))
;; Populates dot-env-environment and returns it.

An additional convenience function is available to easily get a dotenv value:

(dot-env-get (field &optional default))
;; Get the value of FIELD from dot-env-environment.
;; Use DEFAULT if no value is found.
;; Example:
(dot-env-get 'FIELD_NAME "default-value")

If you wish to load your environment from a file other than the default (.emacs.d/.env) you can set the dot-env-filepath variable:

(setq dot-env-filepath "path to your file")
(dot-env-config)

If you have GPG set up on your machine and you want to use an encrypted file as the source of your environment variables, the following will ensure the encrypted values are never stored as plain strings in the Emacs environment.

;; (dot-env-config) is not necessary here
(setq dot-env-filepath "path to your file"
      dot-env-file-is-encrypted t)

;; then access variables like normal
(dot-env-get 'MY_VAR "my-default-value")

Note: this will incur a minor performance hit as the file will need to be fully parsed each time a variable is accessed. As parsing typically only takes place once during initialization, this should not be an issue unless the parsed file is extremely large.

Value in .env file

FONT="DejaVu Sans Mono-11"

Emacs config

;; load the .env file
(dot-env-config)

;; somewhere in your emacs config
(set-frame-font (dot-env-get 'FONT "DejaVu Sans Mono-13") nil t)

The above code changes the font to DejaVu Sans Mono-11. If no value had been specified in the .env file, DejaVu Sans Mono-13 would have been loaded instead.

• It’s easiest just to use the default name and location for the .env file - .env in your .emacs.d directory.
• You should add the name/path of your .env file to your .gitignore file.

The parsing logic is identical with the original but there are some minor differences in function signatures and functionality due to the differences between node.js and Emacs environments:

1. The option to specify the file encoding of the .env file has been left out because Emacs handles this automatically.
2. The option to specify an arbitrary `target` argument to the `populate()` method has been left out. Due to the convention of enabling lexical binding in elisp code, there is no way to pass a variable by reference. The ablity to populate a target which is passed into the function, as it exists in the original library, isn’t possible in elisp code.
3. The `(dot-env-config)` function does not take a debug option as the error that triggers the message that the debug option would’ve enabled prints to the message buffer automatically.
4. The `debug` option has been left out of `(dot-env-parse)` because, while the option exists in the original library’s documentation, it isn’t actually used anywhere in the `parse()` method code.