modenv is a tool to update and keep consistent multiple .env files. It is designed with these objectives in mind:

Simple and intuitive user experience. modenv greatly prioritizes a minimal, intuitive user-interface, helpful error messages and command suggestions to make it easy to use for beginners and experts.
Lighting fast. modenv is written in Rust, compiled natively, and therefore extremely fast.
Error resistant. modenv offers dry-runs and does not perform destructive operations without explicit confirmation.
Composable. modenv uses reasonable error codes, so it can be used effectively in a CI/CD pipeline or build scripts.

Installation

cargo install modenv

Quickstart

Initialize your environment

modenv init

This command creates .env, env.example, and .env.production files, and adds .env* to your gitignore file.

Add to the environment

modenv -a PORT=3000 HOST=0.0.0.0

This command adds PORT=5000 and HOST=0.0.0.0 to the first default env file found, typically .env. The -a flag causes it to add PORT and HOST with blank values to all other env files found. If the key already exists, this operation will fail unless -f is also passed. The default env files are .env.local, .env.development, and .env.

Add to the production environment

Next, add values to .env.production (specified by -p):

modenv -p HOST=0.0.0.0 PORT=5000

Check consistency of your env files

modenv check

This command checks for missing values from your env files. It uses a single file as the reference file, but you can specify another file (e.g. -x for .env.example). This command returns non-zero if there are missing keys, so it can be used as part of a CI/CD pipeline. If you want to update files with blank values for missing keys:

modenv check -f

This command additionally will replicate comments and ordering from the reference file to the other files.