Environment variables

Environment variables are system specified variables that depends on the host system. Software would read it from the system and adjust their behavior. The variables are usually strings and names are UPPERCASED.

Setting Environment Variables

Many systems has built-in way to set them, Some has dashboard to set them e.g. AWS ElasticBeanstalk, Vercel and Netlify. IntelliJ based IDEs also has a place to put them.

In Linux systems, they can be put into ~/.bashrc -file.

export VARIABLE_NAME="value"

Development Setup

Use Docker and set them in .env -file or directly in the configuration.

Production Setup

It is recommended to use .env -files that are loaded to application. A third-party package to load them might be needed, usually need to be performed only once in the program start and shouldn't change until the program is restarted.

VARIABLE_NAME=value

Notice that quotation marks are not used!

An alternative to using dotenv, perhaps better in some cases is to load configuration from json or yaml.

Reading Environment Variables

Many programming languages have a way to read them e.g. in Python

import os

VARIABLE_NAME: str = os.environ['VARIABLE_NAME']

Never put default values, since it causes bugs. If you want default values for development environments, put them directly into Docker configurations.

Conversion to other data types

Since the values are always strings, we need to convert them to other types

import os

def to_bool(value: str) -> bool:
    """
    Returns True if value is 'True'.
    """
    return value == 'True'

DEBUG: bool = to_bool(os.environ['DEBUG'])
MAX_CONNECTIONS: int = int(os.environ['MAX_CONNECTIONS'])