How do I load environment vairibale in .env automatically?

[ylbeethoven]

Hi,

This tool is great for loading flake.nix or shell.nix but it is not clear how it could work like the standard direnv which loads .env automatically.

When I tried direnv allow, I am getting.

error .envrc file not found

Do I have to use a shell.nix to load environment variable?

[bbenne10]

Just add the environment variable to your mkShell invocation. All non-recognized keys provided in the attrset argument given to mkShell will be exported as environment variables inside the spawned shell.

[ylbeethoven]

Just add the environment variable to your mkShell invocation. All non-recognized keys will be exported as environment variables.

Thanks for the reply.

I guess this confirms that this tool can not be used to load .env directly.

Do you mind sharing an simple example? I know below works but I am not too sure if it is the best way to do it.

# save this as shell.nix
{ pkgs ? import <nixpkgs> {}}:

pkgs.mkShell {
    shellHook = ''
      export VAR_NAME=abc
    '';
}

[bbenne10]

We also don't reset the environment entirely. If your .envrc looks like this:

export FOO="bar"
export BAR="baz"
use flake

You'll end up with FOO and BAR in your environment.

You could also add dotenv_if_exists .env to load an existing .env file in the same directory as .envrc.

This is not a nix-direnv bug (or feature) and so I am closing this ticket,

[bbenne10]

Do you mind sharing an simple example?

Not at all:

# save this as shell.nix
{ pkgs ? import <nixpkgs> {}}:

pkgs.mkShell {
    FOO="bar";
}

nix-direnv is not the tool that will be doing the .env loading. direnv does that. We simply provide an additional set of variables to load (or unset). This is really an intersection of three tools and their behaviors:

• mkShell supports setting environment variables by passing unknown keys to it.
• nix-direnv loads the output of a mkShell invocation and so we can "reexport" those variables.
• direnv itself also has more support for handling environment variables, which is kind of the point of the tool :p