SD_JOURNAL_GET_CURSOR(3) sd_journal_get_cursor SD_JOURNAL_GET_CURSOR(3)NAME
sd_journal_get_cursor, sd_journal_test_cursor - Get cursor string for or test cursor string against the current journal entry
int sd_journal_get_cursor(sd_journal* j, char ** cursor);
int sd_journal_test_cursor(sd_journal* j, const char * cursor);
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 failure.
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-journal pkg-config(1) file.
SEE ALSO systemd(1), sd-journal(3), sd_journal_open(3), sd_journal_seek_cursor(3)systemd 208SD_JOURNAL_GET_CURSOR(3)
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SD_JOURNAL_OPEN(3) sd_journal_open SD_JOURNAL_OPEN(3)NAME
sd_journal_open, sd_journal_open_directory, sd_journal_open_files, sd_journal_close, sd_journal, SD_JOURNAL_LOCAL_ONLY,
SD_JOURNAL_RUNTIME_ONLY, SD_JOURNAL_SYSTEM, SD_JOURNAL_CURRENT_USER - Open the system journal for reading
int sd_journal_open(sd_journal** ret, int flags);
int sd_journal_open_directory(sd_journal** ret, const char* path, int flags);
int sd_journal_open_files(sd_journal** ret, const char** paths, int flags);
void sd_journal_close(sd_journal* j);
sd_journal_open() opens the log journal for reading. It will find all journal files automatically and interleave them automatically when
reading. As first argument it takes a pointer to a sd_journal pointer, which on success will contain a journal context object. The second
argument is a flags field, which may consist of the following flags ORed together: SD_JOURNAL_LOCAL_ONLY makes sure only journal files
generated on the local machine will be opened. SD_JOURNAL_RUNTIME_ONLY makes sure only volatile journal files will be opened, excluding
those which are stored on persistent storage. SD_JOURNAL_SYSTEM will cause journal files of system services and the kernel (in opposition
to user session processes) to be opened. SD_JOURNAL_CURRENT_USER will cause journal files of the current user to be opened. If neither
SD_JOURNAL_SYSTEM nor SD_JOURNAL_CURRENT_USER are specified, all journal file types will be opened.
sd_journal_open_directory() is similar to sd_journal_open() but takes an absolute directory path as argument. All journal files in this
directory will be opened and interleaved automatically. This call also takes a flags argument, but it must be passed as 0 as no flags are
currently understood for this call.
sd_journal_open_files() is similar to sd_journal_open() but takes a NULL-terminated list of file paths to open. All files will be opened
and interleaved automatically. This call also takes a flags argument, but it must be passed as 0 as no flags are currently understood for
this call. Please note that in the case of a live journal, this function is only useful for debugging, because individual journal files can
be rotated at any moment, and the opening of specific files is inherently racy.
sd_journal objects cannot be used in the child after a fork. Functions which take a journal object as an argument (sd_journal_next() and
others) will return -ECHILD after a fork.
sd_journal_close() will close the journal context allocated with sd_journal_open() or sd_journal_open_directory() and free its resources.
When opening the journal only journal files accessible to the calling user will be opened. If journal files are not accessible to the
caller, this will be silently ignored.
See sd_journal_next(3) for an example of how to iterate through the journal after opening it with sd_journal_open().
A journal context object returned by sd_journal_open() references a specific journal entry as current entry, similar to a file seek index
in a classic file system file, but without absolute positions. It may be altered with sd_journal_next(3) and sd_journal_seek_head(3) and
related calls. The current entry position may be exported in cursor strings, as accessible via sd_journal_get_cursor(3). Cursor strings may
be used to globally identify a specific journal entry in a stable way and then later to seek to it (or if the specific entry is not
available locally, to its closest entry in time) sd_journal_seek_cursor(3).
Notification of journal changes is available via sd_journal_get_fd() and related calls.
The sd_journal_open(), sd_journal_open_directory(), and sd_journal_open_files() calls return 0 on success or a negative errno-style error
code. sd_journal_close() returns nothing.
The sd_journal_open(), sd_journal_open_directory() and sd_journal_close() interfaces are available as a shared library, which can be
compiled and linked to with the libsystemd-journal pkg-config(1) file.
sd_journal_open(), sd_journal_close(), SD_JOURNAL_LOCAL_ONLY, SD_JOURNAL_RUNTIME_ONLY, SD_JOURNAL_SYSTEM_ONLY were added in systemd-38.
sd_journal_open_directory() was added in systemd-187.
SD_JOURNAL_SYSTEM, SD_JOURNAL_CURRENT_USER, and sd_journal_open_files() were added in systemd-205. SD_JOURNAL_SYSTEM_ONLY was deprecated.
SEE ALSO systemd(1), sd-journal(3), sd_journal_next(3), sd_journal_get_data(3)systemd 208SD_JOURNAL_OPEN(3)