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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_JOURNAL_GET_SEQNUM(3) sd_journal_get_seqnum SD_JOURNAL_GET_SEQNUM(3)
sd_journal_get_seqnum - Read sequence number from the current
journal entry
#include <systemd/sd-journal.h>
int sd_journal_get_seqnum(sd_journal *j, uint64_t *ret_seqnum,
sd_id128_t *ret_seqnum_id);
sd_journal_get_seqnum() returns the sequence number of the
current journal entry. It takes three arguments: the journal
context object, a pointer to a 64-bit unsigned integer to store
the sequence number in, and a buffer to return the 128-bit
sequence number ID in.
When writing journal entries to disk each systemd-journald
instance will number them sequentially, starting from 1 for the
first entry written after subsystem initialization. Each such
series of sequence numbers is associated with a 128-bit sequence
number ID which is initialized randomly, once at systemd-journal
initialization. Thus, while multiple instances of
systemd-journald will assign the same sequence numbers to their
written journal entries, they will have a distinct sequence
number IDs. The sequence number is assigned at the moment of
writing the entry to disk. If log entries are rewritten (for
example because the volatile logs from /run/log/ are flushed to
/var/log/ via systemd-journald-flush.service) they will get new
sequence numbers assigned.
Sequence numbers may be used to order entries (entries associated
with the same sequence number ID and lower sequence numbers
should be ordered chronologically before those with higher
sequence numbers), and to detect lost entries. Note that journal
service instances typically write to multiple journal files in
parallel (for example because SplitMode= is used), in which case
each journal file will only contain a subset of the sequence
numbers. To recover the full stream of journal entries the files
must be combined ("interleaved"), a process that primarily relies
on the sequence numbers. When journal files are rotated (due to
size or time limits), the series of sequence numbers is continued
in the replacement files. All journal files generated from the
same journal instance will carry the same sequence number ID.
As the sequence numbers are assigned at the moment of writing the
journal entries to disk they do not exist if storage is disabled
via SplitMode=.
The ret_seqnum and ret_seqnum_id parameters may be specified as
NULL in which case the relevant data is not returned (but the
call will otherwise succeed).
Note that these functions will not work before sd_journal_next(3)
(or related call) has been called at least once, in order to
position the read pointer at a valid entry.
sd_journal_get_seqnum() returns 0 on success or a negative
errno-style error code..
All functions listed here are thread-agnostic and only a single
specific thread may operate on a given object during its entire
lifetime. It's safe to allocate multiple independent objects and
use each from a specific thread in parallel. However, it's not
safe to allocate such an object in one thread, and operate or
free it from any other, even if locking is used to ensure these
threads don't operate on it at the very same time.
Functions described here are available as a shared library, which
can be compiled against and linked to with the
libsystemd pkg-config(1) file.
sd_journal_get_seqnum() was added in version 254.
systemd(1), sd-journal(3), sd_journal_open(3),
sd_journal_next(3), sd_journal_get_data(3),
sd_journal_get_monotonic_usec(3)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http:https://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http:https://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2023-12-22. (At that
time, the date of the most recent commit that was found in the
repository was 2023-12-22.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 255 SD_JOURNAL_GET_SEQNUM(3)
Pages that refer to this page: sd_journal_get_realtime_usec(3), systemd.directives(7), systemd.index(7), systemd.journal-fields(7)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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