SD_JOURNAL_OPEN(3) sd_journal_open SD_JOURNAL_OPEN(3)
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.
systemd(1), sd-journal(3), sd_journal_next(3), sd_journal_get_data(3)
systemd 208 SD_JOURNAL_OPEN(3)