x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_JOURNAL_ENUMERATE_FIELDsd_journal_enumerate_fSD_JOURNAL_ENUMERATE_FIELDS(3)
NAME
sd_journal_enumerate_fields, sd_journal_restart_fields,
SD_JOURNAL_FOREACH_FIELD - Read used field names from the journal
SYNOPSIS
#include <systemd/sd-journal.h>
int sd_journal_enumerate_fields(sd_journal *j, const char **field);
void sd_journal_restart_fields(sd_journal *j);
SD_JOURNAL_FOREACH_FIELD(sd_journal *j, const char *field);
DESCRIPTION
sd_journal_enumerate_fields() may be used to iterate through all field
names used in the opened journal files. On each invocation the next
field name is returned. The order of the returned field names is not
defined. It takes two arguments: the journal context object, plus a
pointer to a constant string pointer where the field name is stored in.
The returned data is in a read-only memory map and is only valid until
the next invocation of sd_journal_enumerate_fields(). Note that this
call is subject to the data field size threshold as controlled by
sd_journal_set_data_threshold().
sd_journal_restart_fields() resets the field name enumeration index to
the beginning of the list. The next invocation of
sd_journal_enumerate_fields() will return the first field name again.
The SD_JOURNAL_FOREACH_FIELD() macro may be used as a handy wrapper
around sd_journal_restart_fields() and sd_journal_enumerate_fields().
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 retrieve the possible values a specific field can take use
sd_journal_query_unique(3).
RETURN VALUE
sd_journal_enumerate_fields() returns a positive integer if the next
field name has been read, 0 when no more field names are known, or a
negative errno-style error code. sd_journal_restart_fields() 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.
EXAMPLES
Use the SD_JOURNAL_FOREACH_FIELD() macro to iterate through all field
names in use in the current 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 char *field;
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;
}
SD_JOURNAL_FOREACH_FIELD(j, field)
printf("%s\n", field);
sd_journal_close(j);
return 0;
}
SEE ALSO
systemd(1), systemd.journal-fields(7), sd-journal(3),
sd_journal_open(3), sd_journal_query_unique(3), sd_journal_get_data(3),
sd_journal_add_match(3)
systemd 254 SD_JOURNAL_ENUMERATE_FIELDS(3)
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