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.
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
All functions listed here are thread-agnostic and only a single
thread may operate on a given sd_journal object.
The sd_journal_get_cursor() and sd_journal_test_cursor() interfaces
are available as a shared library, which can be compiled and linked
to with the libsystemd pkg-config(1) file.
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systemd 233 SD_JOURNAL_GET_CURSOR(3)