Basics

Given a hello world example, click on the end of each line to get an explanation:

devenv.nix

{ pkgs, ... }: # ``devenv.nix`` is a function with inputs. `pkgs` is an [input](/inputs/) passed as a special argument to the function.

{ # Our function is returning an attribute set, similar to an object in JSON.
  env.GREET = "hello"; # Attributes can be nested and have similar values as in JSON.

  packages = [ pkgs.jq ];

  enterShell = ''
    echo $GREET
    jq --version
  ''; # Values can refer to the inputs. See [Inputs](/inputs/) for how to define inputs.
}

We use a special input ... at the end as a catch-all to avoid enumerating all of the inputs. 2. Our function is returning an attribute set, similar to an object in JSON. 3. Attributes can be nested and have similar values as in JSON. 4. Values can refer to the inputs. See Inputs for how to define inputs.

enterShell allows you to execute bash code once the shell activates, while env allows you to set environment variables.

Consider using tasks instead

For more complex setup operations, consider using tasks instead of enterShell. Tasks provide better control over execution order, dependencies, and can run in parallel:

$ devenv shell
Building shell ...
Entering shell ...

hello
jq-1.6

(devenv) $ echo $GREET
hello

See Nix language tutorial for a 1-2 hour deep dive that will allow you to read any Nix file.

Environment Summary

If you’d like to print the summary of the current environment:

$ devenv info
...

# env
- DEVENV_DOTFILE: .../myproject/.devenv
- DEVENV_ROOT: .../myproject
- DEVENV_STATE: .../myproject/.devenv/state
- GREET: hello

# packages
- jq-1.6

# scripts

# processes