mirror of
https://github.com/systemd/systemd-stable.git
synced 2024-12-23 17:34:00 +03:00
167 lines
6.6 KiB
XML
167 lines
6.6 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
|
||
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
||
|
||
<!--
|
||
SPDX-License-Identifier: LGPL-2.1+
|
||
|
||
This file is part of systemd.
|
||
|
||
Copyright 2016 Lennart Poettering
|
||
|
||
systemd is free software; you can redistribute it and/or modify it
|
||
under the terms of the GNU Lesser General Public License as published by
|
||
the Free Software Foundation; either version 2.1 of the License, or
|
||
(at your option) any later version.
|
||
|
||
systemd is distributed in the hope that it will be useful, but
|
||
WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||
Lesser General Public License for more details.
|
||
|
||
You should have received a copy of the GNU Lesser General Public License
|
||
along with systemd; If not, see <http://www.gnu.org/licenses/>.
|
||
-->
|
||
|
||
<refentry id="sd_journal_enumerate_fields">
|
||
|
||
<refentryinfo>
|
||
<title>sd_journal_enumerate_fields</title>
|
||
<productname>systemd</productname>
|
||
|
||
<authorgroup>
|
||
<author>
|
||
<contrib>Developer</contrib>
|
||
<firstname>Lennart</firstname>
|
||
<surname>Poettering</surname>
|
||
<email>lennart@poettering.net</email>
|
||
</author>
|
||
</authorgroup>
|
||
</refentryinfo>
|
||
|
||
<refmeta>
|
||
<refentrytitle>sd_journal_enumerate_fields</refentrytitle>
|
||
<manvolnum>3</manvolnum>
|
||
</refmeta>
|
||
|
||
<refnamediv>
|
||
<refname>sd_journal_enumerate_fields</refname>
|
||
<refname>sd_journal_restart_fields</refname>
|
||
<refname>SD_JOURNAL_FOREACH_FIELD</refname>
|
||
<refpurpose>Read used field names from the journal</refpurpose>
|
||
</refnamediv>
|
||
|
||
<refsynopsisdiv>
|
||
<funcsynopsis>
|
||
<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_journal_enumerate_fields</function></funcdef>
|
||
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
||
<paramdef>const char **<parameter>field</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>void <function>sd_journal_restart_fields</function></funcdef>
|
||
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef><function>SD_JOURNAL_FOREACH_FIELD</function></funcdef>
|
||
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
||
<paramdef>const char *<parameter>field</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
</funcsynopsis>
|
||
</refsynopsisdiv>
|
||
|
||
<refsect1>
|
||
<title>Description</title>
|
||
|
||
<para><function>sd_journal_enumerate_fields()</function> 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 <function>sd_journal_enumerate_fields()</function>. Note that this call is subject to the data field
|
||
size threshold as controlled by <function>sd_journal_set_data_threshold()</function>.</para>
|
||
|
||
<para><function>sd_journal_restart_fields()</function> resets the field name enumeration index to the beginning of
|
||
the list. The next invocation of <function>sd_journal_enumerate_fields()</function> will return the first field
|
||
name again.</para>
|
||
|
||
<para>The <function>SD_JOURNAL_FOREACH_FIELD()</function> macro may be used as a handy wrapper around
|
||
<function>sd_journal_restart_fields()</function> and <function>sd_journal_enumerate_fields()</function>.</para>
|
||
|
||
<para>These functions currently are not influenced by matches set with <function>sd_journal_add_match()</function>
|
||
but this might change in a later version of this software.</para>
|
||
|
||
<para>To retrieve the possible values a specific field can take use
|
||
<citerefentry><refentrytitle>sd_journal_query_unique</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Return Value</title>
|
||
|
||
<para><function>sd_journal_enumerate_fields()</function> 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.
|
||
<function>sd_journal_restart_fields()</function> returns
|
||
nothing.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Notes</title>
|
||
|
||
<para>All functions listed here are thread-agnostic and only a single thread may operate
|
||
on a given <structname>sd_journal</structname> object.</para>
|
||
|
||
<para>The <function>sd_journal_enumerate_fields()</function> and <function>sd_journal_restart_fields()</function>
|
||
interfaces are available as a shared library, which can be compiled and linked to with the
|
||
<constant>libsystemd</constant> <citerefentry
|
||
project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Examples</title>
|
||
|
||
<para>Use the <function>SD_JOURNAL_FOREACH_FIELD</function> macro to iterate through all field names in use in the
|
||
current journal.</para>
|
||
|
||
<programlisting>#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;
|
||
}</programlisting>
|
||
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>See Also</title>
|
||
|
||
<para>
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_journal_query_unique</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|