import { LogWriter, LogEntry } from '..';
/**
 * Log writer that appends each entry to a file as a single line of JSON (NDJSON).
 * Writes are synchronous (`appendFileSync`) so entries are durable even when the
 * process exits hard via `process.exit()`. The parent directory is created on demand.
 */
export declare class FileWriter implements LogWriter {
    private readonly fileName;
    private directoryEnsured;
    constructor(fileName: string);
    format({ level, time, category, message }: LogEntry): string;
    write(entry: LogEntry): void;
}
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