Ubuntu Manpage: sd_journal_get_cursor, sd_journal_test_cursor

Provided by: libsystemd-dev_256.5-2ubuntu3_amd64

NAME

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

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);

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).

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.

Note that sd_journal_get_cursor() and sd_journal_test_cursor() will not work before
sd_journal_next(3) (or one of the other functions which move to an entry) has been called
at least once to position the read pointer at a valid entry.

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.

NOTES

       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.

       Functions described here are available as a shared library, which can be compiled against
       and linked to with the libsystemd pkg-config(1) file.

HISTORY