What is env-cmd?
The env-cmd npm package allows you to easily set environment variables from a file or inline before running a command. This is particularly useful for managing different environments (development, testing, production) without hardcoding environment variables in your code.
What are env-cmd's main functionalities?
Load environment variables from a file
This feature allows you to load environment variables from a specified file before running your command. The file should follow the standard .env format.
env-cmd -f ./path/to/.env node app.js
Load environment variables from multiple files
You can load environment variables from multiple files. This is useful for layering configurations, such as having a base configuration and an environment-specific override.
env-cmd -f ./path/to/.env -f ./path/to/.env.local node app.js
Inline environment variables
This feature allows you to set environment variables inline directly in the command. This is useful for quick tests or temporary overrides.
env-cmd -e 'NODE_ENV=production' node app.js
JSON configuration
You can also pass environment variables as a JSON object. This is useful for more complex configurations that might be easier to manage in JSON format.
env-cmd -e '{"NODE_ENV": "production", "API_KEY": "12345"}' node app.js
Other packages similar to env-cmd
dotenv
dotenv is a popular package for loading environment variables from a .env file into process.env. Unlike env-cmd, dotenv is typically used by requiring it in your code, rather than as a command-line tool.
cross-env
cross-env allows you to set environment variables across different platforms (Windows, Linux, macOS) in a consistent manner. It is similar to env-cmd but focuses more on cross-platform compatibility.
dotenv-cli
dotenv-cli is a command-line interface for dotenv, allowing you to load environment variables from a .env file before running a command, similar to env-cmd. It provides a simpler interface but lacks some of the advanced features of env-cmd.

env-cmd
A simple node program for executing commands using an environment from an env file.
💾 Install
npm install env-cmd
or npm install -g env-cmd
⌨️ Basic Usage
Environment file ./.env
# This is a comment
ENV1=THANKS
ENV2=FOR ALL
ENV3=THE FISH
Package.json
{
"scripts": {
"test": "env-cmd mocha -R spec"
}
}
Terminal
./node_modules/.bin/env-cmd node index.js
Using custom env file path
To use a custom env filename or path, pass the -f
flag. This is a major breaking change from prior versions < 9.0.0
Terminal
./node_modules/.bin/env-cmd -f ./custom/path/.env node index.js
📜 Help
Usage: _ [options] <command> [...args]
Options:
-v, --version output the version number
-e, --environments [env1,env2,...] The rc file environment(s) to use
-f, --file [path] Custom env file path (default path: ./.env)
--fallback Fallback to default env file path, if custom env file path not found
--no-override Do not override existing environment variables
-r, --rc-file [path] Custom rc file path (default path: ./.env-cmdrc(|.js|.json)
--silent Ignore any env-cmd errors and only fail on executed program failure.
--use-shell Execute the command in a new shell with the given environment
--verbose Print helpful debugging information
-x, --expand-envs Replace $var in args and command with environment variables
-h, --help output usage information
🔬 Advanced Usage
.rc
file usage
For more complex projects, a .env-cmdrc
file can be defined in the root directory and supports
as many environments as you want. Simply use the -e
flag and provide which environments you wish to
use from the .env-cmdrc
file. Using multiple environment names will merge the environment variables
together. Later environments overwrite earlier ones in the list if conflicting environment variables
are found.
.rc file ./.env-cmdrc
{
"development": {
"ENV1": "Thanks",
"ENV2": "For All"
},
"test": {
"ENV1": "No Thanks",
"ENV3": "!"
},
"production": {
"ENV1": "The Fish"
}
}
Terminal
./node_modules/.bin/env-cmd -e production node index.js
./node_modules/.bin/env-cmd -e test,production node index.js
--no-override
option
Prevents overriding of existing environment variables on process.env
and within the current
environment.
--fallback
file usage option
If the .env
file does not exist at the provided custom path, then use the default
fallback location ./.env
env file instead.
--use-shell
Executes the command within a new shell environment. This is useful if you want to string multiple
commands together that share the same environment variables.
Terminal
./node_modules/.bin/env-cmd -f ./test/.env --use-shell "npm run lint && npm test"
Asynchronous env file support
EnvCmd supports reading from asynchronous .env
files. Instead of using a .env
file, pass in a .js
file that exports either an object or a Promise
resolving to an object ({ ENV_VAR_NAME: value, ... }
). Asynchronous .rc
files are also supported using .js
file extension and resolving to an object with top level environment
names ({ production: { ENV_VAR_NAME: value, ... } }
).
Terminal
./node_modules/.bin/env-cmd -f ./async-file.js node index.js
-x
expands vars in arguments
EnvCmd supports expanding $var
values passed in as arguments to the command. The allows a user
to provide arguments to a command that are based on environment variable values at runtime.
Terminal
./node_modules/.bin/env-cmd -x node index.js --user=$USER
--silent
suppresses env-cmd errors
EnvCmd supports the --silent
flag the suppresses all errors generated by env-cmd
while leaving errors generated by the child process and cli signals still usable. This
flag is primarily used to allow env-cmd
to run in environments where the .env
file might not be present, but still execute the child process without failing
due to a missing file.
💿 Examples
You can find examples of how to use the various options above by visiting
the examples repo env-cmd-examples.
💽️ Environment File Formats
These are the currently accepted environment file formats. If any other formats are desired please create an issue.
.env
as key=value
.env.json
Key/value pairs as JSON
.env.js
JavaScript file exporting an object
or a Promise
that resolves to an object
.env-cmdrc
as valid json or .env-cmdrc.json
in execution directory with at least one environment { "dev": { "key1": "val1" } }
.env-cmdrc.js
JavaScript file exporting an object
or a Promise
that resolves to an object
that contains at least one environment
🗂 Path Rules
This lib attempts to follow standard bash
path rules. The rules are as followed:
Home Directory = /Users/test
Working Directory = /Users/test/Development/app
Absolute | /some/absolute/path.env | /some/absolute/path.env |
Home Directory with ~ | ~/starts/on/homedir/path.env | /Users/test/starts/on/homedir/path.env |
Relative | ./some/relative/path.env or some/relative/path.env | /Users/test/Development/app/some/relative/path.env |
Relative with parent dir | ../some/relative/path.env | /Users/test/Development/some/relative/path.env |
🛠 API Usage
EnvCmd
A function that executes a given command in a new child process with the given environment and options
options
{ object
}
command
{ string
}: The command to execute (node
, mocha
, ...)
commandArgs
{ string[]
}: List of arguments to pass to the command
(['-R', 'Spec']
)
envFile
{ object
}
filePath
{ string
}: Custom path to .env file to read from (defaults to: ./.env
)
fallback
{ boolean
}: Should fall back to default ./.env
file if custom path does not exist
rc
{ object
}
environments
{ string[]
}: List of environment to read from the .rc
file
filePath
{ string
}: Custom path to the .rc
file (defaults to: ./.env-cmdrc(|.js|.json)
)
options
{ object
}
expandEnvs
{ boolean
}: Expand $var
values passed to commandArgs
(default: false
)
noOverride
{ boolean
}: Prevent .env
file vars from overriding existing process.env
vars (default: false
)
silent
{ boolean
}: Ignore any errors thrown by env-cmd, used to ignore missing file errors (default: false
)
useShell
{ boolean
}: Runs command inside a new shell instance (default: false
)
verbose
{ boolean
}: Prints extra debug logs to console.info
(default: false
)
- Returns {
Promise<object>
}: key is env var name and value is the env var value
GetEnvVars
A function that parses environment variables from a .env
or a .rc
file
options
{ object
}
envFile
{ object
}
filePath
{ string
}: Custom path to .env file to read from (defaults to: ./.env
)
fallback
{ boolean
}: Should fall back to default ./.env
file if custom path does not exist
rc
{ object
}
environments
{ string[]
}: List of environment to read from the .rc
file
filePath
{ string
}: Custom path to the .rc
file (defaults to: ./.env-cmdrc(|.js|.json)
)
verbose
{ boolean
}: Prints extra debug logs to console.info
(default: false
)
- Returns {
Promise<object>
}: key is env var name and value is the env var value
🧙 Why
Because sometimes it is just too cumbersome passing a lot of environment variables to scripts. It is
usually just easier to have a file with all the vars in them, especially for development and testing.
🚨Do not commit sensitive environment data to a public git repo! 🚨
🧬 Related Projects
cross-env
- Cross platform setting of environment scripts
🎊 Special Thanks
Special thanks to cross-env
for inspiration (uses the
same cross-spawn
lib underneath too).
📋 Contributing Guide
I welcome all pull requests. Please make sure you add appropriate test cases for any features
added. Before opening a PR please make sure to run the following scripts:
npm run lint
checks for code errors and format according to ts-standard
npm test
make sure all tests pass
npm run test-cover
make sure the coverage has not decreased from current master