This Emacs major mode is designed for viewing the output from systemd’s journalctl within Emacs. It provides a convenient way to interact with journalctl logs, including features like fontification, chunked loading for performance, and custom keyword highlighting.

To install, place journalctl-mode.el in your load-path and add the following to your .emacs file:

(require 'journalctl-mode)

Alternatively, you can install journalctl-mode using the use-package macro with Quelpa for automatic installation from the GitHub repository:

(use-package journalctl-mode
  :ensure t)

It might be a good idea to define a global key to journalctl with:

(global-set-key (kbd "C-c t") 'journalctl)

or with use-package:

(use-package journalctl-mode
  :ensure t
  :bind (("C-c t" . journalctl)))

• Fontification: Customize the appearance of log levels with faces.
• Chunked Loading: Load journalctl output in manageable chunks for better performance.
• Keyword Highlighting: Define custom keywords for error, warning, and other log levels.
• Follow Mode: Simulate tail -f functionality to keep up with new log entries.

Once installed, journalctl-mode can be invoked with M-x journalctl. The mode provides a transient interface for journalctl command-line options, allowing for dynamic and flexible log viewing.

Customize the mode to your liking by setting the following variables:

• journalctl-chunk-size: Number of lines per chunk (default 250).
• journalctl-error-keywords: List of keywords to highlight as errors.
• journalctl-warn-keywords: List of keywords to highlight as warnings.
• journalctl-starting-keywords: Keywords for starting processes.
• journalctl-finished-keywords: Keywords for finished processes.
• journalctl-follow-freq: Frequency for updating in follow mode.
• journalctl-follow-lines: Number of lines to show in follow mode.
• journalctl-default-options: List of default options for journalctl on start.

There is another package journalctl (rather than journalctl-mode) by James Ferguson that fetches and interleaves JSON data using multiple simultaneous asynchronous journalctl queries, while mine offers a UI for query-building and chunked synchronous data loading.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.

For support, feedback, or to contribute to the project, please visit the homepage at https://github.com/SebastianMeisel/journalctl-mode.

Thanks to all contributors and users for their support and feedback which continue to improve this mode.