..
   This file is part of Logtalk <https://logtalk.org/>
   SPDX-FileCopyrightText: 1998-2026 Paulo Moura <pmoura@logtalk.org>
   SPDX-License-Identifier: Apache-2.0

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.


.. rst-class:: align-right

**built-in method**

.. index:: pair: message_prefix_file/6; Built-in method
.. _methods_message_prefix_file_6:

``message_prefix_file/6``
=========================

Description
-----------

::

   message_prefix_file(Kind, Component, Prefix, File, Mode, Options)

Experimental user-defined hook method for specifying the prefix and file
for copying messages for a given kind and :term:`component`. This method
is declared in the :ref:`logtalk <apis:logtalk/0>` built-in object as a
public, multifile, and dynamic predicate. The valid values for ``Mode``
are ``write`` and ``append``. The valid options are the same as the
standard ``open/4`` predicate.

The prefix is printed for each line in the list of tokens generated by the
message tokenization (new lines are specified using the ``nl`` token; see
the documentation of the :ref:`logtalk <apis:logtalk/0>` built-in object
for details).

Modes and number of proofs
--------------------------

::

   message_prefix_file(?nonvar, ?nonvar, ?atom, ?atom, ?atom, ?list(compound)) - zero_or_more

Errors
------

(none)

Examples
--------

::

   :- multifile(logtalk::message_prefix_file/6).
   :- dynamic(logtalk::message_prefix_file/6).

   logtalk::message_prefix_file(comment, app, '% ', 'comments.txt', append, []).

.. seealso::

   :ref:`methods_message_prefix_stream_4`,
   :ref:`methods_message_hook_4`,
   :ref:`methods_message_tokens_2`,
   :ref:`methods_print_message_3`,
   :ref:`methods_print_message_tokens_3`,
   :ref:`methods_print_message_token_4`,
   :ref:`methods_ask_question_5`,
   :ref:`methods_question_hook_6`,
   :ref:`methods_question_prompt_stream_4`
