|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
SD_JOURNAL_ENUMERATE_FIELDS(3)urnal_enumerate_fieldsRNAL_ENUMERATE_FIELDS(3)
sd_journal_enumerate_fields, sd_journal_restart_fields,
SD_JOURNAL_FOREACH_FIELD - Read used field names from the journal
#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);
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).
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.
All functions listed here are thread-agnostic and only a single
thread may operate on a given sd_journal object.
The sd_journal_enumerate_fields() and sd_journal_restart_fields()
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_FIELD macro to iterate through all field
names in use in the current journal.
#include <stdio.h>
#include <string.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) {
fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
return 1;
}
SD_JOURNAL_FOREACH_FIELD(j, field)
printf("%s\n", field);
sd_journal_close(j);
return 0;
}
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)
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⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
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COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
systemd 234 SD_JOURNAL_ENUMERATE_FIELDS(3)
Pages that refer to this page: sd-journal(3), sd_journal_query_unique(3), systemd.directives(7), systemd.index(7)