Environment Variables (std::env)

Reads PATH, applies a default with ??, sets APP_NAME, and then removes it.

// Feature: env.get / env.set — environment variables
// When to use: env-driven config (12-factor), feature flags, secrets.

use std::env

// env.get(name) -> string or nil if not present.
let path = env.get("PATH")
print(path != nil)  // expected: true

let missing = env.get("VARIABLE_THAT_DOES_NOT_EXIST_42")
print(missing)  // expected: nil

// Idiomatic pattern: default via `??`.
let port = env.get("APP_PORT") ?? "8080"
print(port)  // expected: 8080 (if APP_PORT not set)

// env.set(name, value) modifies the current process environment.
env.set("APP_NAME", "zolo")
print(env.get("APP_NAME"))  // expected: zolo

// env.remove undoes it.
env.remove("APP_NAME")
print(env.get("APP_NAME"))  // expected: nil

Requires the Zolo CLI/host — open in the playground or run locally.

Reads PATH from env.all(), prints OS, architecture, and home directory.

// Feature: env.all / env.os / env.arch / env.home_dir — environment info
// When to use: cross-platform scripts, debugging, picking paths per OS.

use std::Map
use std::env

// env.all() -> plain table mapping VAR=value. Use Map.from to wrap
// it in a Map object, or index it directly with `[name]`.
let all = env.all()
let path = all["PATH"]
let has_path = path != nil
print(has_path)  // expected: true

// Current OS: "windows", "linux", "macos".
// (`os` shadows the Lua-builtin module of the same name; pick a
// different identifier to be safe.)
let cur_os = env.os()
print(cur_os.len() > 0)  // expected: true

// Architecture: "x64", "arm64", etc.
let cur_arch = env.arch()
print(cur_arch.len() > 0)  // expected: true

// User's home directory (nil only on very unusual setups).
let home = env.home_dir()
let has_home = home != nil
print(has_home)  // expected: true

Requires the Zolo CLI/host — open in the playground or run locally.

Defines Config with port, log_level, debug, and database_url via environment variables.

// Feature: env — idiomatic pattern for loading configuration
// When to use: 12-factor applications read config from env vars.

use std::string
use std::env

// Define a config struct to centralize all defaults.
struct Config {
  port: int,
  log_level: str,
  debug: bool,
  database_url: str,
}

fn parse_int(s: str?, default_v: int) -> int {
  if s == nil { return default_v }
  let n = string::to_int(s)
  if n == nil { return default_v }
  return n
}

fn parse_bool(s: str?) -> bool {
  if s == nil { return false }
  return s == "true" || s == "1" || s == "yes"
}

fn load_config() -> Config {
  return Config { port: parse_int(env.get("APP_PORT"), 8080), log_level: env.get("APP_LOG_LEVEL") ?? "info", debug: parse_bool(env.get("APP_DEBUG")), database_url: env.get("DATABASE_URL") ?? "postgres://localhost/dev" }
}

let cfg = load_config()
print(cfg.port)  // expected: 8080 (default)
print(cfg.log_level)  // expected: info (default)

Requires the Zolo CLI/host — open in the playground or run locally.