1SD_JOURNAL_GET_CURSOR(3) sd_journal_get_cursor SD_JOURNAL_GET_CURSOR(3)
2
6 sd_journal_get_cursor, sd_journal_test_cursor - Get cursor string for
7 or test cursor string against the current journal entry
8
10 #include <systemd/sd-journal.h>
11 int sd_journal_get_cursor(sd_journal *j, char **cursor);
13 int sd_journal_test_cursor(sd_journal *j, const char *cursor);
15
17 sd_journal_get_cursor() returns a cursor string for the current journal
18 entry. A cursor is a serialization of the current journal position
19 formatted as text. The string only contains printable characters and
20 can be passed around in text form. The cursor identifies a journal
21 entry globally and in a stable way and may be used to later seek to it
22 via sd_journal_seek_cursor(3). The cursor string should be considered
23 opaque and not be parsed by clients. Seeking to a cursor position
24 without the specific entry being available locally will seek to the
25 next closest (in terms of time) available entry. The call takes two
26 arguments: a journal context object and a pointer to a string pointer
27 where the cursor string will be placed. The string is allocated via
28 libc malloc(3) and should be freed after use with free(3).
29 Note that sd_journal_get_cursor() will not work before
31 sd_journal_next(3) (or related call) has been called at least once, in
32 order to position the read pointer at a valid entry.
33 sd_journal_test_cursor() may be used to check whether the current
35 position in the journal matches the specified cursor. This is useful
36 since cursor strings do not uniquely identify an entry: the same entry
37 might be referred to by multiple different cursor strings, and hence
38 string comparing cursors is not possible. Use this call to verify after
39 an invocation of sd_journal_seek_cursor(3) whether the entry being
40 sought to was actually found in the journal or the next closest entry
41 was used instead.
42
44 sd_journal_get_cursor() returns 0 on success or a negative errno-style
45 error code. sd_journal_test_cursor() returns positive if the current
46 entry matches the specified cursor, 0 if it does not match the
47 specified cursor or a negative errno-style error code on failure.
48
50 All functions listed here are thread-agnostic and only a single
51 specific thread may operate on a given object during its entire
52 lifetime. It's safe to allocate multiple independent objects and use
53 each from a specific thread in parallel. However, it's not safe to
54 allocate such an object in one thread, and operate or free it from any
55 other, even if locking is used to ensure these threads don't operate on
56 it at the very same time.
57 These APIs are implemented as a shared library, which can be compiled
59 and linked to with the libsystemd pkg-config(1) file.
60
62 systemd(1), sd-journal(3), sd_journal_open(3),
63 sd_journal_seek_cursor(3)
64systemd 241 SD_JOURNAL_GET_CURSOR(3)