json_env

json_env is dotenv, but with JSON. It loads an environment variables from a JSON file (.env.json per default) and starts a subprocess with them. Storing configuration in the environment separate from code is based on The Twelve-Factor App methodology.

How to install

With homebrew:

$ brew tap brodo/json_env
$ brew install json_env

With NPM

$ npm i -g @brodo/json_env

With cargo:

$ cargo install json_env

Or download the binaries for your platform on the releases page and put them in your $PATH.

How to use

Just run json_env with any program as a parameter:

$ json_env my_program

Additional command line arguments that are passed to json_env are forwarded to the child process:

$ json_env echo "Test"

Test

Example

.env.json:

{
    "NODE_ENV": "DEV",
    "MY_USER": "Carl",
    "NUM_USERS": 10,
    "nested": {
        "hello": "world",
        "boo": "far"
    }
}

Shell:

$ json_env env

MY_USER=Carl
NODE_ENV=DEV
NUM_USERS=10
nested={"boo":"far","hello":"world"}
[...]

Environment Variable Expansion

You can include existing environment variables in your env file to expand them:

.env.json:

{
  "MY_VAR": "$FOO",
  "MY_OTHER_VAR": "User:$USER"
}

Shell:

$ json_env -e env
FOO=Bar
USER=Carl
MY_VAR=Bar
MY_OTHER_VAR=User:Carl
[...]

JSON Path support

There are some use cases where you already have environment variables defined in a JSON file but not at the root level. Take this Azure Function local.settings.json file for example:

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "<language worker>",
    "AzureWebJobsStorage": "<connection-string>",
    "MyBindingConnection": "<binding-connection-string>",
    "AzureWebJobs.HttpExample.Disabled": "true"
  },
  "Host": {
    "LocalHttpPort": 7071,
    "CORS": "*",
    "CORSCredentials": false
  },
  "ConnectionStrings": {
    "SQLConnectionString": "<sqlclient-connection-string>"
  }
}

The Values property contains the environment variables we are interested in. You can use this file to run app.js with the environment variables defined in Values by providing the JSON Path `$.Values``:

$ json_env -c local.settings.json -p $.Values node app.js

License

json_env is licensed under the Apache 2.0 license.