x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_JOURNAL_OPEN(3) sd_journal_open SD_JOURNAL_OPEN(3)
NAME
sd_journal_open, sd_journal_open_directory,
sd_journal_open_directory_fd, sd_journal_open_files,
sd_journal_open_files_fd, sd_journal_open_namespace, sd_journal_close,
sd_journal, SD_JOURNAL_LOCAL_ONLY, SD_JOURNAL_RUNTIME_ONLY,
SD_JOURNAL_SYSTEM, SD_JOURNAL_CURRENT_USER, SD_JOURNAL_OS_ROOT,
SD_JOURNAL_ALL_NAMESPACES, SD_JOURNAL_INCLUDE_DEFAULT_NAMESPACE,
SD_JOURNAL_TAKE_DIRECTORY_FD - Open the system journal for reading
SYNOPSIS
#include <systemd/sd-journal.h>
int sd_journal_open(sd_journal **ret, int flags);
int sd_journal_open_namespace(sd_journal **ret, const char *namespace,
int flags);
int sd_journal_open_directory(sd_journal **ret, const char *path,
int flags);
int sd_journal_open_directory_fd(sd_journal **ret, int fd, int flags);
int sd_journal_open_files(sd_journal **ret, const char **paths,
int flags);
int sd_journal_open_files_fd(sd_journal **ret, int fds[],
unsigned n_fds, int flags);
void sd_journal_close(sd_journal *j);
DESCRIPTION
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_namespace() is similar to sd_journal_open() but takes
an additional namespace parameter that specifies which journal
namespace to operate on. If specified as NULL the call is identical to
sd_journal_open(). If non-NULL only data from the namespace identified
by the specified parameter is accessed. This call understands two
additional flags: if SD_JOURNAL_ALL_NAMESPACES is specified the
namespace parameter is ignored and all defined namespaces are accessed
simultaneously; if SD_JOURNAL_INCLUDE_DEFAULT_NAMESPACE the specified
namespace and the default namespace are accessed but no others (this
flag has no effect when namespace is passed as NULL). For details about
journal namespaces see systemd-journald.service(8).
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. The flags parameters accepted by this call are
SD_JOURNAL_OS_ROOT, SD_JOURNAL_SYSTEM, and SD_JOURNAL_CURRENT_USER. If
SD_JOURNAL_OS_ROOT is specified, journal files are searched for below
the usual /var/log/journal and /run/log/journal relative to the
specified path, instead of directly beneath it. The other two flags
limit which files are opened, the same as for sd_journal_open().
sd_journal_open_directory_fd() is similar to
sd_journal_open_directory(), but takes a file descriptor referencing a
directory in the file system instead of an absolute file system path.
In addition to the flags accepted by sd_journal_open_directory(), this
function also accepts SD_JOURNAL_TAKE_DIRECTORY_FD. If
SD_JOURNAL_TAKE_DIRECTORY_FD is specified, the function will take the
ownership of the specified file descriptor on success, and it will be
closed by sd_journal_close(), hence the caller of the function must not
close the file descriptor. When the flag is not specified,
sd_journal_close() will not close the file descriptor, so the caller
should close it after sd_journal_close().
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_open_files_fd() is similar to sd_journal_open_files() but
takes an array of open file descriptors that must reference journal
files, instead of an array of file system paths. Pass the array of file
descriptors as second argument, and the number of array entries in the
third. The flags parameter must be passed as 0.
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.
RETURN VALUE
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.
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.
SEE ALSO
systemd(1), sd-journal(3), systemd-journald.service(8),
sd_journal_next(3), sd_journal_get_data(3)
systemd 254 SD_JOURNAL_OPEN(3)
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