|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
SD_JOURNAL_QUERY_UNIQUE(3) sd_journal_query_uniqueSD_JOURNAL_QUERY_UNIQUE(3)
sd_journal_query_unique, sd_journal_enumerate_unique,
sd_journal_restart_unique, SD_JOURNAL_FOREACH_UNIQUE - Read unique
data fields from the journal
#include <systemd/sd-journal.h>
int sd_journal_query_unique(sd_journal *j, const char *field);
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);
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). 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(). Invoking this call a second time 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 context
object, plus a pair of pointers to pointer/size variables where the
data object and its size shall be stored in. 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().
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_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.
sd_journal_query_unique() returns 0 on success or a negative
errno-style error code. sd_journal_enumerate_unique() returns a
positive integer if the next field data has been read, 0 when no more
fields are known, or a negative errno-style error code.
sd_journal_restart_unique() returns nothing.
All functions listed here are thread-agnostic and only a single
thread may operate on a given sd_journal object.
The sd_journal_query_unique(), sd_journal_enumerate_unique() and
sd_journal_restart_unique() interfaces are available as a shared
library, which can be compiled and linked to with the
libsystemd pkg-config(1) file.
Use the SD_JOURNAL_FOREACH_UNIQUE macro to iterate through all values
a field of the journal can take. The following example lists all unit
names referenced in the journal:
#include <stdio.h>
#include <string.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) {
fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
return 1;
}
r = sd_journal_query_unique(j, "_SYSTEMD_UNIT");
if (r < 0) {
fprintf(stderr, "Failed to query journal: %s\n", strerror(-r));
return 1;
}
SD_JOURNAL_FOREACH_UNIQUE(j, d, l)
printf("%.*s\n", (int) l, (const char*) d);
sd_journal_close(j);
return 0;
}
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)
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2017-07-05. If you dis‐
cover any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
systemd 234 SD_JOURNAL_QUERY_UNIQUE(3)
Pages that refer to this page: sd-journal(3), sd_journal_enumerate_fields(3), sd_journal_get_data(3), systemd.directives(7), systemd.index(7)