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sd_journal_get_seqnum(3) — Linux manual page

SD_JOURNAL_GET_SEQNUM(3)  sd_journal_get_seqnumSD_JOURNAL_GET_SEQNUM(3)

NAME        top

       sd_journal_get_seqnum - Read sequence number from the current       journal entry

SYNOPSIS        top

#include <systemd/sd-journal.h>int sd_journal_get_seqnum(sd_journal *j, uint64_t *ret_seqnum,sd_id128_t *ret_seqnum_id);

DESCRIPTION        top

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 eachsystemd-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 atsystemd-journal       initialization. Thus, while multiple instances ofsystemd-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 becauseSplitMode= 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       viaSplitMode=.       Theret_seqnum andret_seqnum_id parameters may be specified asNULLin which case the relevant data is not returned (but the call       will otherwise succeed).       Note that these functions will not work beforesd_journal_next(3)       (or related call) has been called at least once, in order to       position the read pointer at a valid entry.

RETURN VALUE        top

sd_journal_get_seqnum()returns 0 on success or a negative       errno-style error code..

NOTES        top

       All functions listed here are thread-agnostic and only a single       specific thread may operate on a given object during its entire       lifetime. It is safe to allocate multiple independent objects and       use each from a specific thread in parallel. However, it is 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       do not 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 thelibsystemd pkg-config(1) file.

HISTORY        top

sd_journal_get_seqnum()was added in version 254.

SEE ALSO        top

systemd(1),sd-journal(3),sd_journal_open(3),sd_journal_next(3),sd_journal_get_data(3),sd_journal_get_monotonic_usec(3)

COLOPHON        top

       This page is part of thesystemd (systemd system and service       manager) project.  Information about the project can be found at       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a       bug report for this manual page, see       ⟨http://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 2025-08-11.  (At that       time, the date of the most recent commit that was found in the       repository was 2025-08-11.)  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 isnot part of the original manual page), send a mail to       man-pages@man7.orgsystemd 258~rc2SD_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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