Environment Variables with ard/env

The ard/env module provides functions for reading environment variables from the operating system.

The env module provides:

• Environment variable access with the get function
• Maybe type returns for safe handling of undefined variables

use ard/env
use ard/io

fn main() {
  match env::get("HOME") {
    path => io::print("Home directory: {path}"),
    _ => io::print("HOME not set")
  }
}

API

fn get(name: Str) Str?

Get the value of an environment variable by name. Returns a Maybe type - some if the variable is set, none if it’s not.

use ard/env

let home = env::get("HOME")

Examples

Access a Single Environment Variable

use ard/env
use ard/io

fn main() {
  match env::get("USER") {
    user => io::print("User: {user}"),
    _ => io::print("USER not set")
  }
}

Use Default Value if Not Set

use ard/env

fn main() {
  let debug_mode = env::get("DEBUG").or("false")
  io::print("Debug mode: {debug_mode}")
}

Check Multiple Environment Variables

use ard/env
use ard/io

fn main() {
  let host = env::get("DB_HOST").or("localhost")
  let port = env::get("DB_PORT").or("5432")
  let user = env::get("DB_USER").or("postgres")

  io::print("Database: {user}@{host}:{port}")
}

Build Configuration from Environment

use ard/env
use ard/io

struct Config {
  api_url: Str,
  api_key: Str,
  timeout: Str
}

fn main() {
  let config = Config {
    api_url: env::get("API_URL").or("https://api.example.com"),
    api_key: env::get("API_KEY").or(""),
    timeout: env::get("REQUEST_TIMEOUT").or("30")
  }

  io::print("API URL: {config.api_url}")
}

Validate Required Environment Variables

use ard/env
use ard/io

fn main() {
  match env::get("DATABASE_URL") {
    url => {
      io::print("Using database: {url}")
    },
    _ => {
      io::print("ERROR: DATABASE_URL environment variable not set")
    }
  }
}