import type { AnyCaller } from "./function.js";
/**
 * Get a `process.env` variable safely in all environments, or `undefined` if it doesn't exist or this environment does not support `process.env` (i.e. web environments).
 */
export declare function getEnv(name: string): string | undefined;
/**
 * Get a `process.env` variable safely in all environments, or throw `RequiredError` if it doesn't exist or this environment does not support `process.env` (i.e. web environments).
 */
export declare function requireEnv(name: string, caller?: AnyCaller): string;
/**
 * Get a `process.env` variable and resolve it to to `true` or `false`, or `undefined` if it isn't a true/false value.
 */
export declare function getEnvBoolean(name: string): boolean | undefined;
/**
 * Get a `process.env` variable and resolve it to to `true` or `false`
 *
 * @returns `false` if the environment variable is `0`, `off`, `no`, `false`
 * @returns `true` if the environment variable is `1`, `on`, `yes`, `true`
 * @throws `RequiredError` if the env variable is any other value.
 */
export declare function requireEnvBoolean(name: string, caller?: AnyCaller): boolean;