journald writes binary log files; and their format is explicitly subject to change.
The Journald Reference Guide tells us, quote:
While it can be useful to get used to journalctl to read logs, it’s by no means mandatory.
So, how can we read these files? Is there a journald reading API I missed? I couldn't find any yet.
On
Update: https://github.com/meta-bit/jjournal does the job for me, Java API for the purpose.
HTH
Systemd (and journald) are written in C. They come with
sd-journal.hheader file and with C-API https://www.freedesktop.org/software/systemd/man/sd_journal_next.html# -sd_journal_openallows you to open logs and then read from them.Other languages - https://www.freedesktop.org/software/systemd/python-systemd/journal.html#example-polling-for-journal-events https://github.com/nyantec/rust-journald - most probably build on top of the C api.
Moreover, journald is open source - https://github.com/systemd/systemd/blob/968680b23d1629d33deeea98b4f2b5fd106075b5/src/libsystemd/sd-journal/sd-journal.c#L1916 - and the file format is documented - https://www.freedesktop.org/wiki/Software/systemd/journal-files/ . You can re-implement your own API on top of system-specific I/O operations to read journal files.