type Callback = (code?: number | null, signal?: string | null) => void;
/**
 * Registers a callback to be executed when the process exits or receives a termination signal.
 *
 * This function is an internal replacement for the `signal-exit` library.
 * It ensures that the callback is executed when the process ends, whether naturally
 * or via signals like SIGINT (Ctrl+C).
 *
 * @param callback - The function to call on exit.
 * @param options - Configuration options.
 * @param options.alwaysLast - (Ignored in this simplified implementation) Ensures callback runs after other exit handlers.
 * @returns A function to unsubscribe the exit listener.
 */
export declare function onExit(callback: Callback): () => void;
export {};