sd_journal_get_cursor(3) — Linux manual page


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

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),

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, see
       ⟨⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-09-18.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-09-18.)  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

systemd 246                                         SD_JOURNAL_GET_CURSOR(3)

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