x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_JOURNAL_QUERY_UNIQUE(3) sd_journal_query_unique SD_JOURNAL_QUERY_UNIQUE(3)
NAME
sd_journal_query_unique, sd_journal_enumerate_unique,
sd_journal_enumerate_available_unique, sd_journal_restart_unique,
SD_JOURNAL_FOREACH_UNIQUE - Read unique data fields from the journal
SYNOPSIS
#include <systemd/sd-journal.h>
int sd_journal_query_unique(sd_journal *j, const char *field);
int sd_journal_enumerate_available_unique(sd_journal *j,
const void **data,
size_t *length);
int sd_journal_enumerate_unique(sd_journal *j, const void **data,
size_t *length);
void sd_journal_restart_unique(sd_journal *j);
SD_JOURNAL_FOREACH_UNIQUE(sd_journal *j, const void *data,
size_t length);
DESCRIPTION
sd_journal_query_unique() queries the journal for all unique values the
specified field can take. It takes two arguments: the journal to query
and the field name to look for. Well-known field names are listed on
systemd.journal-fields(7), but any field can be specified. Field names
must be specified without a trailing "=". After this function has been
executed successfully the field values may be queried using
sd_journal_enumerate_unique() and
sd_journal_enumerate_available_unique(). Invoking one of those calls
will change the field name being queried and reset the enumeration
index to the first field value that matches.
sd_journal_enumerate_unique() may be used to iterate through all data
fields which match the previously selected field name as set with
sd_journal_query_unique(). On each invocation the next field data
matching the field name is returned. The order of the returned data
fields is not defined. It takes three arguments: the journal object,
plus a pair of pointers to pointer/size variables where the data object
and its size shall be stored. The returned data is in a read-only
memory map and is only valid until the next invocation of
sd_journal_enumerate_unique(). Note that the data returned will be
prefixed with the field name and "=". Note that this call is subject to
the data field size threshold as controlled by
sd_journal_set_data_threshold() and only the initial part of the field
up to the threshold is returned. An error is returned for fields which
cannot be retrieved. See the error list below for details.
sd_journal_enumerate_available_unique() is similar to
sd_journal_enumerate_unique(), but silently skips any fields which may
be valid, but are too large or not supported by current implementation.
sd_journal_restart_unique() resets the data enumeration index to the
beginning of the list. The next invocation of
sd_journal_enumerate_unique() will return the first field data matching
the field name again.
Note that the SD_JOURNAL_FOREACH_UNIQUE() macro may be used as a handy
wrapper around sd_journal_restart_unique() and
sd_journal_enumerate_available_unique().
Note that these functions currently are not influenced by matches set
with sd_journal_add_match() but this might change in a later version of
this software.
To enumerate all field names currently in use (and thus all suitable
field parameters for sd_journal_query_unique()), use the
sd_journal_enumerate_fields(3) call.
RETURN VALUE
sd_journal_query_unique() returns 0 on success or a negative
errno-style error code. sd_journal_enumerate_unique() and
sd_journal_query_available_unique() return a positive integer if the
next field data has been read, 0 when no more fields remain, or a
negative errno-style error code. sd_journal_restart_unique() doesn't
return anything.
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.
-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
Use the SD_JOURNAL_FOREACH_UNIQUE() macro to iterate through all values
a field of the journal can take (and which can be accessed on the given
architecture and are not compressed with an unsupported mechanism). The
following example lists all unit names referenced in the journal:
/* SPDX-License-Identifier: MIT-0 */
#include <errno.h>
#include <stdio.h>
#include <systemd/sd-journal.h>
int main(int argc, char *argv[]) {
sd_journal *j;
const void *d;
size_t l;
int r;
r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY);
if (r < 0) {
errno = -r;
fprintf(stderr, "Failed to open journal: %m\n");
return 1;
}
r = sd_journal_query_unique(j, "_SYSTEMD_UNIT");
if (r < 0) {
errno = -r;
fprintf(stderr, "Failed to query journal: %m\n");
return 1;
}
SD_JOURNAL_FOREACH_UNIQUE(j, d, l)
printf("%.*s\n", (int) l, (const char*) d);
sd_journal_close(j);
return 0;
}
SEE ALSO
systemd(1), systemd.journal-fields(7), sd-journal(3),
sd_journal_open(3), sd_journal_enumerate_fields(3),
sd_journal_get_data(3), sd_journal_add_match(3)
systemd 254 SD_JOURNAL_QUERY_UNIQUE(3)
Want to link to this manual page? Use this URL:
<http://star2.abcm.com/cgi-bin/bsdi-man?query=sd_journal_query_unique&sektion=3&manpath=>