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 file.truncate()
    except Exception as e:
        print("Exception while updating bookmark file:", e)
        return None

    # Call filter_log_data to filter the copied data
    filtered_filename = filter_log_data(filename)

    # Compress the output file and remove the uncompressed file
    output_file_name = output_file.name
    new_output_file_name = output_file_name.replace('.txt', '-cassandra.log')
    os.rename(output_file_name, new_output_file_name)
    try:
        with open(new_output_file_name, 'rb') as input_file, gzip.open(new_output_file_name + '.gz', 'wb') as output_file_gz:
            input_data = input_file.read()
            output_file_gz.write(input_data)
            os.remove(new_output_file_name)
            # Set permissions on the output file
            os.chmod(output_file_gz.name, 0o777)

    except Exception as e:
        print("Exception while compressing file:", e)

    # Return the filtered filename
    return filtered_filename