x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_JOURNAL_GET_DATA(3) sd_journal_get_data SD_JOURNAL_GET_DATA(3)
NAME
sd_journal_get_data, sd_journal_enumerate_data,
sd_journal_enumerate_available_data, sd_journal_restart_data,
SD_JOURNAL_FOREACH_DATA, sd_journal_set_data_threshold,
sd_journal_get_data_threshold - Read data fields from the current
journal entry
SYNOPSIS
#include <systemd/sd-journal.h>
int sd_journal_get_data(sd_journal *j, const char *field,
const void **data, size_t *length);
int sd_journal_enumerate_data(sd_journal *j, const void **data,
size_t *length);
int sd_journal_enumerate_available_data(sd_journal *j,
const void **data,
size_t *length);
void sd_journal_restart_data(sd_journal *j);
SD_JOURNAL_FOREACH_DATA(sd_journal *j, const void *data,
size_t length);
int sd_journal_set_data_threshold(sd_journal *j, size_t sz);
int sd_journal_get_data_threshold(sd_journal *j, size_t *sz);
DESCRIPTION
sd_journal_get_data() gets the data object associated with a specific
field from the current journal entry. It takes four arguments: the
journal context object, a string with the field name to request, plus a
pair of pointers to pointer/size variables where the data object and
its size shall be stored in. The field name should be an entry field
name. Well-known field names are listed in systemd.journal-fields(7),
but any field can be specified. The returned data is in a read-only
memory map and is only valid until the next invocation of
sd_journal_get_data(), sd_journal_enumerate_data(),
sd_journal_enumerate_available_data(), or when the read pointer is
altered. Note that the data returned will be prefixed with the field
name and "=". Also note that, by default, data fields larger than 64K
might get truncated to 64K. This threshold may be changed and turned
off with sd_journal_set_data_threshold() (see below).
sd_journal_enumerate_data() may be used to iterate through all fields
of the current entry. On each invocation the data for the next field is
returned. The order of these fields is not defined. The data returned
is in the same format as with sd_journal_get_data() and also follows
the same life-time semantics.
sd_journal_enumerate_available_data() is similar to
sd_journal_enumerate_data(), but silently skips any fields which may be
valid, but are too large or not supported by current implementation.
sd_journal_restart_data() resets the data enumeration index to the
beginning of the entry. The next invocation of
sd_journal_enumerate_data() will return the first field of the entry
again.
Note that the SD_JOURNAL_FOREACH_DATA() macro may be used as a handy
wrapper around sd_journal_restart_data() and
sd_journal_enumerate_available_data().
Note that these functions 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_set_data_threshold() may be used to change the data field
size threshold for data returned by sd_journal_get_data(),
sd_journal_enumerate_data() and sd_journal_enumerate_unique(). This
threshold is a hint only: it indicates that the client program is
interested only in the initial parts of the data fields, up to the
threshold in size -- but the library might still return larger data
objects. That means applications should not rely exclusively on this
setting to limit the size of the data fields returned, but need to
apply an explicit size limit on the returned data as well. This
threshold defaults to 64K by default. To retrieve the complete data
fields this threshold should be turned off by setting it to 0, so that
the library always returns the complete data objects. It is recommended
to set this threshold as low as possible since this relieves the
library from having to decompress large compressed data objects in
full.
sd_journal_get_data_threshold() returns the currently configured data
field size threshold.
RETURN VALUE
sd_journal_get_data() returns 0 on success or a negative errno-style
error code. sd_journal_enumerate_data() and
sd_journal_enumerate_available_data() return a positive integer if the
next field has been read, 0 when no more fields remain, or a negative
errno-style error code. sd_journal_restart_data() doesn't return
anything. sd_journal_set_data_threshold() and
sd_journal_get_threshold() return 0 on success or a negative
errno-style error code.
Errors
Returned errors may indicate the following problems:
-EINVAL
One of the required parameters is NULL or invalid.
-ECHILD
The journal object was created in a different process, library or
module instance.
-EADDRNOTAVAIL
The read pointer is not positioned at a valid entry;
sd_journal_next(3) or a related call has not been called at least
once.
-ENOENT
The current entry does not include the specified field.
-ENOMEM
Memory allocation failed.
-ENOBUFS
A compressed entry is too large.
-E2BIG
The data field is too large for this computer architecture (e.g.
above 4 GB on a 32-bit architecture).
-EPROTONOSUPPORT
The journal is compressed with an unsupported method or the journal
uses an unsupported feature.
-EBADMSG
The journal is corrupted (possibly just the entry being iterated
over).
-EIO
An I/O error was reported by the kernel.
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.
EXAMPLES
See sd_journal_next(3) for a complete example how to use
sd_journal_get_data().
Use the SD_JOURNAL_FOREACH_DATA() macro to iterate through all fields
of the current journal entry:
...
int print_fields(sd_journal *j) {
const void *data;
size_t length;
SD_JOURNAL_FOREACH_DATA(j, data, length)
printf("%.*s\n", (int) length, data);
}
...
SEE ALSO
systemd(1), systemd.journal-fields(7), sd-journal(3),
sd_journal_open(3), sd_journal_next(3),
sd_journal_get_realtime_usec(3), sd_journal_query_unique(3)
systemd 254 SD_JOURNAL_GET_DATA(3)
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