Introduction to direnv

direnv is a powerful extension for your shell that manages your environment variables. It is an essential tool for developers who need to manage multiple projects with different configurations. This guide covers dozens of useful direnv APIs and provides an application example to help you get started.

Getting Started with direnv

To install direnv, you can use the following command:

  brew install direnv

Basic Usage

Add the following line to your shell configuration file (.bashrc, .zshrc, etc.) to enable direnv:

  eval "$(direnv hook bash)"

Creating a .envrc File

The .envrc file is where you define the environment variables for a project. Here is an example:

  export NODE_ENV=development
  export DATABASE_URL=postgres://localhost/mydb

Loading .envrc Automatically

To allow direnv to automatically load the .envrc file, run:

  direnv allow

Common API Methods

Here are several useful API methods provided by direnv:

use_node

Set up Node.js version automatically:

  use node 14

use_python

Set up Python version automatically:

  use python 3.8

layout_go

Set up Go environment automatically:

  layout go

path_add

Add a directory to your PATH:

  path_add bin

dotenv

Load environment variables from a .env file:

  dotenv

Custom Environment Variables

You can define your own functions in the .envrc file:

  layout_project() {
    export PROJECT_DIR=$(pwd)
    path_add $PROJECT_DIR/bin
  }

  layout_project

Application Example

Here is an example of a simple Node.js application configured with direnv:

Project Structure

  my-node-app/
  ├── .envrc
  ├── .env
  ├── bin/
  ├── node_modules/
  ├── package.json
  └── app.js

.envrc File

  use node 14
  dotenv
  export API_KEY=abcdef123456

.env File

  DATABASE_URL=postgres://localhost/mydb

app.js File

  const dotenv = require('dotenv');
  dotenv.config();

  const apiKey = process.env.API_KEY;
  const dbUrl = process.env.DATABASE_URL;

  console.log('API Key:', apiKey);
  console.log('Database URL:', dbUrl);

Run your application:

  node app.js

With this configuration, direnv will automatically set up your environment variables, making it easier to manage your development workflow.

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