direnv

name	direnv
description	Guide for using direnv - a shell extension for loading directory-specific environment variables. Use when setting up project environments, creating .envrc files, configuring per-project environment variables, integrating with Python/Node/Ruby/Go layouts, working with Nix flakes, or troubleshooting environment loading issues on macOS and Linux.

direnv Skill

Shell extension for loading and unloading environment variables based on the current directory.

Overview

direnv enables:

• Per-project environment configurations
• Automatic loading of 12-factor app environment variables
• Isolated development environments with language-specific layouts
• Secure allowlist-based security model
• Integration with Nix, asdf, and version managers

Quick Start

Installation

# macOS
brew install direnv

# Linux (Debian/Ubuntu)
sudo apt install direnv

# Linux (binary)
curl -sfL https://direnv.net/install.sh | bash

# Verify
direnv version

Shell Hook Configuration

Zsh (~/.zshrc):

eval "$(direnv hook zsh)"

Bash (~/.bashrc):

eval "$(direnv hook bash)"

Fish (~/.config/fish/config.fish):

direnv hook fish | source

Place hook at end of file, after other shell extensions.

Basic Usage

# Create .envrc
echo 'export MY_VAR=value' > .envrc

# Allow the .envrc (required for security)
direnv allow

# Block an .envrc
direnv deny

# Force reload
direnv reload

# Check status
direnv status

Essential Commands

Command	Description
direnv allow [path]	Allow/trust an .envrc file
direnv deny [path]	Revoke trust from .envrc
direnv reload	Force reload current .envrc
direnv status	Show current direnv state
direnv edit	Open .envrc in $EDITOR
direnv prune	Remove expired/revoked .envrc
direnv version	Show installed version

Standard Library (stdlib)

direnv includes a powerful stdlib. Use these functions instead of raw exports.

PATH Management

# Add to PATH (prepends safely)
PATH_add bin
PATH_add node_modules/.bin
PATH_add scripts

# Add multiple paths
PATH_add bin scripts tools

# Remove from PATH
PATH_rm "*/.git/bin"

Environment File Loading

# Load .env file
dotenv

# Load specific file
dotenv .env.local

# Load if exists (no error if missing)
dotenv_if_exists .env.local

# Load parent .envrc
source_up

# Load specific .envrc
source_env ../.envrc

# Load if exists
source_env_if_exists .envrc.local

Language Layouts

# Python - creates virtualenv in .direnv/
layout python
layout python3
layout python python3.11

# Node.js - adds node_modules/.bin to PATH
layout node

# Ruby - sets GEM_HOME
layout ruby

# Go - configures GOPATH
layout go

# Perl - local::lib
layout perl

# Pipenv
layout pipenv

Nix Integration

# Load nix-shell environment
use nix

# Load Nix flake
use flake

# Specific flake
use flake "nixpkgs#hello"

For better flakes support: nix-direnv

Version Managers

# rbenv
use rbenv

# Node.js (fuzzy matching)
use node 18
use node 18.17.0

# From .nvmrc
use node

Validation

# Require variables
env_vars_required API_KEY DATABASE_URL

# Watch for file changes
watch_file package.json
watch_file config/*.yaml
watch_dir config

# Check git branch
if on_git_branch main; then
  export DEPLOY_ENV=production
fi

# Minimum version
direnv_version 2.32.0

# Strict mode (exit on errors)
strict_env

Recommended .envrc Template

#!/usr/bin/env bash
# .envrc - Project environment configuration

# Enforce direnv version
direnv_version 2.32.0

# Load .env file if exists
dotenv_if_exists

# Load local overrides (not committed)
source_env_if_exists .envrc.local

# Language-specific layout
layout node
# or: layout python3

# Add project paths
PATH_add bin
PATH_add scripts

# Development settings
export NODE_ENV=development
export LOG_LEVEL=debug

# Watch configuration files
watch_file package.json
watch_file .tool-versions

Project Structure Best Practice

my-project/
├── .envrc           # Development environment (committed)
├── .envrc.local     # Local overrides (gitignored)
├── .env             # Environment variables (gitignored)
├── .env.example     # Template for team members (committed)
└── .direnv/         # Cache directory (gitignored)

.gitignore

# Environment files with secrets
.env
.env.local
.envrc.local

# direnv cache
.direnv/

Layered Configuration

Use parent directory inheritance:

# ~/projects/.envrc (global dev settings)
export EDITOR=vim
export PAGER=less

# ~/projects/api/.envrc
source_up  # Inherit from parent
export API_PORT=3000
layout node

# ~/projects/api/feature-x/.envrc
source_up  # Inherit from api
export FEATURE_FLAG=true

Custom Extensions

Create at ~/.config/direnv/direnvrc:

# ~/.config/direnv/direnvrc

# Kubernetes context switcher
use_kubernetes() {
  local context="${1:-default}"
  export KUBECONFIG="${HOME}/.kube/config"
  kubectl config use-context "$context" >/dev/null 2>&1
  log_status "kubernetes context: $context"
}

# AWS profile switcher
use_aws() {
  local profile="${1:-default}"
  export AWS_PROFILE="$profile"
  log_status "aws profile: $profile"
}

# Azure subscription
use_azure() {
  local subscription="$1"
  export AZURE_SUBSCRIPTION="$subscription"
  az account set --subscription "$subscription" >/dev/null 2>&1
  log_status "azure subscription: $subscription"
}

# uv Python layout (modern alternative)
layout_uv() {
  if ! has uv; then
    log_error "uv not found. Install: curl -LsSf https://astral.sh/uv/install.sh | sh"
    return 1
  fi

  VIRTUAL_ENV="$(pwd)/.venv"
  if [[ ! -d "$VIRTUAL_ENV" ]]; then
    uv venv
  fi

  PATH_add "$VIRTUAL_ENV/bin"
  export VIRTUAL_ENV
}

Usage in .envrc:

use kubernetes dev-cluster
use aws production
layout uv

Common Patterns

Python with uv

# .envrc
direnv_version 2.32.0
dotenv_if_exists

# Use uv for Python
if has uv; then
  layout_uv
else
  layout python3
fi

export PYTHONDONTWRITEBYTECODE=1

Node.js Project

# .envrc
direnv_version 2.32.0
dotenv_if_exists
source_env_if_exists .envrc.local

layout node

export NODE_ENV=development
export PORT=3000

watch_file package.json

Kubernetes Development

# .envrc
dotenv_if_exists

use_kubernetes dev-cluster

export KUBECONFIG="${HOME}/.kube/config"
export KUBE_NAMESPACE=my-app

PATH_add bin

Multi-Environment Support

# .envrc
direnv_version 2.32.0

# Determine environment
if on_git_branch main; then
  ENV=production
elif on_git_branch staging; then
  ENV=staging
else
  ENV=development
fi

export APP_ENV="$ENV"

# Load environment-specific config
dotenv_if_exists ".env.$ENV"
source_env_if_exists ".envrc.$ENV"

log_status "environment: $ENV"

Troubleshooting Quick Reference

# Check status
direnv status

# Force reload
direnv reload

# Re-allow .envrc
direnv allow

# Debug environment
direnv dump
direnv show_dump

# Export for debugging
direnv export bash

Common Issues

Issue	Solution
Environment not loading	Run direnv allow
Hook not working	Verify hook in shell config, restart shell
Slow loading	Use nix-direnv for Nix; reduce watch_file calls
Variables not unloading	Check for export -f functions; restart shell

IDE Integration

VS Code

Install direnv extension.

JetBrains IDEs

Install direnv integration plugin.

Emacs

(use-package envrc
  :hook (after-init . envrc-global-mode))

Vim/Neovim

" Use direnv.vim plugin
Plug 'direnv/direnv.vim'

Security Notes

1. Always review .envrc before allowing - direnv executes arbitrary code
2. Never commit secrets - Use .env files in .gitignore
3. Use .envrc.local for sensitive overrides - Keep local, never commit
4. Trust hierarchy - Parent directories can override child settings

References

• references/installation.md - Complete installation guide
• references/stdlib-functions.md - Full stdlib reference
• references/troubleshooting.md - Extended troubleshooting
• Official docs: https://direnv.net/
• Stdlib reference: https://direnv.net/man/direnv-stdlib.1.html
• nix-direnv: https://github.com/nix-community/nix-direnv