export declare function writeFile(fileDest: string, buffer: Buffer, mode?: number): void;
/**
 * Creates a file only if it doesn't already exist, using O_CREAT|O_EXCL.
 * Throws EEXIST if the file was created by another process concurrently.
 * Note: the write itself is not atomic — a crash mid-write can leave a partial file.
 */
export declare function writeFileExclusive(fileDest: string, buffer: Buffer, mode?: number): void;