получить строку курсора или проверить строку курсора относительно текущей записи журнала (Get cursor string for or test cursor string against the current journal entry)
Имя (Name)
sd_journal_get_cursor, sd_journal_test_cursor - Get cursor string
for or test cursor string against the current journal entry
Синопсис (Synopsis)
#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);
Описание (Description)
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.
Возвращаемое значение (Return value)
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.
Примечание (Note)
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.
Смотри также (See also)
systemd(1), sd-journal(3), sd_journal_open(3),
sd_journal_seek_cursor(3)
