sd_journal_get_cursor(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | COLOPHON

SD_JOURNAL_GET_CURSOR(3)  sd_journal_get_cursor SD_JOURNAL_GET_CURSOR(3)

NAME         top

       sd_journal_get_cursor, sd_journal_test_cursor - Get cursor string
       for or test cursor string against the current journal entry

SYNOPSIS         top

       #include <systemd/sd-journal.h>

       int sd_journal_get_cursor(sd_journal *j, char **cursor);

       int sd_journal_test_cursor(sd_journal *j, const char *cursor);

DESCRIPTION         top

       sd_journal_get_cursor() returns a cursor string for the current
       journal entry. A cursor is a serialization of the current journal
       position formatted as text. The string only contains printable
       characters and can be passed around in text form. The cursor
       identifies a journal entry globally and in a stable way and may
       be used to later seek to it via sd_journal_seek_cursor(3). The
       cursor string should be considered opaque and not be parsed by
       clients. Seeking to a cursor position without the specific entry
       being available locally will seek to the next closest (in terms
       of time) available entry. The call takes two arguments: a journal
       context object and a pointer to a string pointer where the cursor
       string will be placed. The string is allocated via libc malloc(3)
       and should be freed after use with free(3).

       Note that sd_journal_get_cursor() 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_test_cursor() may be used to check whether the current
       position in the journal matches the specified cursor. This is
       useful since cursor strings do not uniquely identify an entry:
       the same entry might be referred to by multiple different cursor
       strings, and hence string comparing cursors is not possible. Use
       this call to verify after an invocation of
       sd_journal_seek_cursor(3) whether the entry being sought to was
       actually found in the journal or the next closest entry was used
       instead.

RETURN VALUE         top

       sd_journal_get_cursor() returns 0 on success or a negative
       errno-style error code.  sd_journal_test_cursor() returns
       positive if the current entry matches the specified cursor, 0 if
       it does not match the specified cursor or a negative errno-style
       error code on failure.

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'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.

       These APIs are implemented as a shared library, which can be
       compiled and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       systemd(1), sd-journal(3), sd_journal_open(3),
       sd_journal_seek_cursor(3)

COLOPHON         top

       This page is part of the systemd (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 2021-04-01.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-04-01.)  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
       man-pages@man7.org

systemd 248                                     SD_JOURNAL_GET_CURSOR(3)

Pages that refer to this page: sd-journal(3)sd_journal_next(3)sd_journal_open(3)sd_journal_seek_head(3)systemd.directives(7)systemd.index(7)