env-from-example

Interactive and non-interactive CLI to set up .env from .env.example.

Walks you through each variable, validates types, auto-generates secrets, and prints a summary of what was configured. All type detection and validation are driven by a bundled schema.json.

Quick Start

# Run without installing (npx fetches and runs)
npx @wchen.ai/env-from-example

# After installing in your project, use the short form:
npx env-from-example

# Don't have a .env.example yet? Create one:
npx env-from-example --init            # starter template, add env vars, then polish
npx env-from-example --init .env       # from your existing .env

# Don't have a .env? Generate one from .env.example
npx env-from-example                   # Generate .env
npx env-from-example -e staging        # Generate .env.staging

Installation

Install in your project so you can run npx env-from-example from the project root:

npm install @wchen.ai/env-from-example
# or
pnpm add @wchen.ai/env-from-example
# or as a dev dependency (recommended for CLI tools)
npm install -D @wchen.ai/env-from-example
pnpm add -D @wchen.ai/env-from-example

Then run from your project root: npx env-from-example (or add it to your package.json scripts).

Setup

Add a .env.example in your project root (or run env-from-example --init to create one).

npx env-from-example --init            # starter template
npx env-from-example --init .env       # from your existing .env

Before and after (first run)

If you start with only a .env.example and no .env (or an empty one), running the tool fills in .env from your answers and defaults.

Before — you have .env.example and no .env (or .env is empty):

# .env.example (excerpt)
DATABASE_URL=postgres://localhost:5432/myapp
API_KEY=
NODE_ENV=development
SESSION_SECRET=

# .env — missing or empty

After — run env-from-example (or env-from-example -y to accept defaults). The CLI prompts for required values, can auto-generate secrets (e.g. SESSION_SECRET), and writes:

# .env — created/updated by env-from-example
DATABASE_URL=postgres://localhost:5432/myapp
API_KEY=your-api-key-here
NODE_ENV=development
SESSION_SECRET=a1b2c3d4e5f6...

Use env-from-example -y --dry-run to preview the result without writing files.

Usage

Run from your project root (where .env.example lives):

env-from-example

Options:

Flag	Description
-y, --yes	Non-interactive: accept existing values or defaults without prompting
-f, --force	Force re-run even if .env is already up-to-date
-e, --env <name>	Target environment (e.g., local, test, production)
--cwd <path>	Project root directory (default: current working directory)
--init [source]	Create .env.example from an existing env file or from scratch
--polish	Polish .env.example: add descriptions, types, defaults (-y for non-interactive)
--version [bump]	Bump or set ENV_SCHEMA_VERSION (patch, minor, major, or exact semver)
--sync-package	With --version: also update package.json version
--validate [envFile]	Validate .env against .env.example schema (exit 1 if invalid)
--dry-run	Preview what would be written without creating/modifying files

Examples:

# Interactive setup (default .env)
env-from-example

# Non-interactive: create/update .env with defaults or existing values
env-from-example -y

# Preview what would be generated (no files written)
env-from-example -y --dry-run

# Create .env.local with prompts
env-from-example -e local

# Create .env.test without prompts (e.g. CI)
env-from-example -y -e test

# Force re-run even if .env is up-to-date
env-from-example -f

# Run from another directory (e.g. monorepo package)
env-from-example --cwd ./apps/api

# Override a variable via CLI
env-from-example --database-url "postgres://prod:5432/db" -y

# Bump ENV_SCHEMA_VERSION
env-from-example --version patch
env-from-example --version minor --sync-package

# Validate .env against .env.example schema
env-from-example --validate

Annotations

Each variable in .env.example can be annotated with structured tags in the comment line above it:

# <description> [REQUIRED] [TYPE: <schema-type>] [CONSTRAINTS: key=value,...] Default: <value>
VARIABLE_NAME=default_value

Annotation	Syntax	Purpose
Description	Free text at start of comment	Human-readable explanation
Required	[REQUIRED]	Variable must be non-empty
Type	[TYPE: <schema-type>]	Type from schema.json for validation and detection
Constraints	[CONSTRAINTS: key=value,...]	Constraints (min, max, pattern, etc.)
Default	Default: <value>	Documented default (informational)

All annotations are optional. The --polish command auto-detects and adds them.

Polish: before and after

env-from-example --polish (or --polish -y for non-interactive) updates your .env.example with inferred descriptions, types, and default annotations.

Before — minimal .env.example:

DATABASE_URL=postgres://localhost:5432/myapp
PORT=3000
NODE_ENV=development
API_KEY=

After — run env-from-example --polish -y:

# env-from-example (https://www.npmjs.com/package/@wchen.ai/env-from-example)

# ENV_SCHEMA_VERSION="1.0.0"

# ========================================
#                Database
# ========================================

# Database Url
# [REQUIRED] [TYPE: network/uri] Default: postgres://localhost:5432/myapp
DATABASE_URL=postgres://localhost:5432/myapp

# ========================================
#                  App
# ========================================

# Application port
# [REQUIRED] [TYPE: integer] [CONSTRAINTS: min=3000,max=10000] Default: 3000
PORT=3000

# Node Env
# [TYPE: structured/enum] [CONSTRAINTS: pattern=^(development|test|staging|production|ci)$] Default: development
NODE_ENV=development

# ========================================
#                 Other
# ========================================

# OPEN AI API KEY
# [REQUIRED] [TYPE: credentials/secret] Default: (empty)
API_KEY=

Use env-from-example --polish --dry-run to preview changes without writing the file.

CI / CD

GitHub Actions -- generate .env.test before running tests:

# .github/workflows/test.yml
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm ci
      - run: npx env-from-example -y -e test
      - run: npm test

Pre-commit hook -- validate .env stays in sync:

# .husky/pre-commit
npx env-from-example --validate

Requirements

• A .env.example file in the project root (or the path given by --cwd). Run env-from-example --init to create one.
• schema.json is bundled with the package and used automatically.

License

ISC