mirror of
https://github.com/systemd/systemd.git
synced 2024-11-24 10:43:35 +08:00
217 lines
9.3 KiB
XML
217 lines
9.3 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">
|
||
|
||
<!--
|
||
This file is part of systemd.
|
||
|
||
Copyright 2012 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_add_match">
|
||
|
||
<refentryinfo>
|
||
<title>sd_journal_add_match</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_add_match</refentrytitle>
|
||
<manvolnum>3</manvolnum>
|
||
</refmeta>
|
||
|
||
<refnamediv>
|
||
<refname>sd_journal_add_match</refname>
|
||
<refname>sd_journal_add_disjunction</refname>
|
||
<refname>sd_journal_add_conjunction</refname>
|
||
<refname>sd_journal_flush_matches</refname>
|
||
<refpurpose>Add or remove entry matches</refpurpose>
|
||
</refnamediv>
|
||
|
||
<refsynopsisdiv>
|
||
<funcsynopsis>
|
||
<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_journal_add_match</function></funcdef>
|
||
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
||
<paramdef>const void *<parameter>data</parameter></paramdef>
|
||
<paramdef>size_t <parameter>size</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_journal_add_disjunction</function></funcdef>
|
||
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_journal_add_conjunction</function></funcdef>
|
||
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>void <function>sd_journal_flush_matches</function></funcdef>
|
||
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
||
</funcprototype>
|
||
</funcsynopsis>
|
||
</refsynopsisdiv>
|
||
|
||
<refsect1>
|
||
<title>Description</title>
|
||
|
||
<para><function>sd_journal_add_match()</function> adds a match by
|
||
which to filter the entries of the journal file. Matches applied
|
||
with this call will filter what can be iterated through and read
|
||
from the journal file via calls like
|
||
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
and
|
||
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
||
Parameter <parameter>data</parameter> must be of the form
|
||
<literal><replaceable>FIELD</replaceable>=<replaceable>value</replaceable></literal>,
|
||
where the <replaceable>FIELD</replaceable> part is a short uppercase string consisting only
|
||
of 0–9, A–Z and the underscore; it may not begin with two underscores or be the empty
|
||
string. The <replaceable>value</replaceable> part may be anything, including binary. Parameter
|
||
<parameter>size</parameter> specifies the number of bytes in <parameter>data</parameter>
|
||
(i.e. the length of <replaceable>FIELD</replaceable>, plus one, plus the length of
|
||
<replaceable>value</replaceable>). Parameter <parameter>size</parameter> may also be
|
||
specified as <constant>0</constant>, in which case <parameter>data</parameter>
|
||
must be a <constant>NUL</constant>-terminated string, and the bytes before the terminating
|
||
zero are used as the match.</para>
|
||
|
||
<para>If a match is applied, only entries with this field set
|
||
will be iterated. Multiple matches may be active at the same time:
|
||
If they apply to different fields, only entries with both fields
|
||
set like this will be iterated. If they apply to the same fields,
|
||
only entries where the field takes one of the specified values
|
||
will be iterated. Well known fields are documented in
|
||
<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
|
||
Whenever a new match is added the current entry position is reset,
|
||
and
|
||
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
(or a similar call) needs to be called before entries can be read
|
||
again.</para>
|
||
|
||
<para><function>sd_journal_add_disjunction()</function> may be
|
||
used to insert a disjunction (i.e. logical OR) in the match list.
|
||
If this call is invoked, all previously added matches since the
|
||
last invocation of
|
||
<function>sd_journal_add_disjunction()</function> or
|
||
<function>sd_journal_add_conjunction()</function> are combined in
|
||
an OR with all matches added afterwards, until
|
||
<function>sd_journal_add_disjunction()</function> or
|
||
<function>sd_journal_add_conjunction()</function> is invoked again
|
||
to begin the next OR or AND term. </para>
|
||
|
||
<para><function>sd_journal_add_conjunction()</function> may be
|
||
used to insert a conjunction (i.e. logical AND) in the match list.
|
||
If this call is invoked, all previously added matches since the
|
||
last invocation of
|
||
<function>sd_journal_add_conjunction()</function> are combined in
|
||
an AND with all matches added afterwards, until
|
||
<function>sd_journal_add_conjunction()</function> is invoked again
|
||
to begin the next AND term. The combination of
|
||
<function>sd_journal_add_match()</function>,
|
||
<function>sd_journal_add_disjunction()</function> and
|
||
<function>sd_journal_add_conjunction()</function> may be used to
|
||
build complex search terms, even though full logical expressions
|
||
are not available. Note that
|
||
<function>sd_journal_add_conjunction()</function> operates one
|
||
level 'higher' than
|
||
<function>sd_journal_add_disjunction()</function>. It is hence
|
||
possible to build an expression of AND terms, consisting of OR
|
||
terms, consisting of AND terms, consisting of OR terms of matches
|
||
(the latter OR expression is implicitly created for matches with
|
||
the same field name, see above).</para>
|
||
|
||
<para><function>sd_journal_flush_matches()</function> may be used
|
||
to flush all matches, disjunction and conjunction terms again.
|
||
After this call all filtering is removed and all entries in the
|
||
journal will be iterated again.</para>
|
||
|
||
<para>Note that filtering via matches only applies to the way the
|
||
journal is read, it has no effect on storage on disk.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Return Value</title>
|
||
|
||
<para><function>sd_journal_add_match()</function>,
|
||
<function>sd_journal_add_disjunction()</function> and
|
||
<function>sd_journal_add_conjunction()</function>
|
||
return 0 on success or a negative errno-style error
|
||
code. <function>sd_journal_flush_matches()</function>
|
||
returns nothing.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Notes</title>
|
||
|
||
<para>The <function>sd_journal_add_match()</function>,
|
||
<function>sd_journal_add_disjunction()</function>,
|
||
<function>sd_journal_add_conjunction()</function> and
|
||
<function>sd_journal_flush_matches()</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>The following example adds matches to a journal context
|
||
object to iterate only through messages generated by the Avahi
|
||
service at the four error log levels, plus all messages of the
|
||
message ID 03bb1dab98ab4ecfbf6fff2738bdd964 coming from any
|
||
service (this example lacks the necessary error checking):</para>
|
||
|
||
<programlisting>...
|
||
int add_matches(sd_journal *j) {
|
||
sd_journal_add_match(j, "_SYSTEMD_UNIT=avahi-daemon.service", 0);
|
||
sd_journal_add_match(j, "PRIORITY=0", 0);
|
||
sd_journal_add_match(j, "PRIORITY=1", 0);
|
||
sd_journal_add_match(j, "PRIORITY=2", 0);
|
||
sd_journal_add_match(j, "PRIORITY=3", 0);
|
||
sd_journal_add_disjunction(j);
|
||
sd_journal_add_match(j, "MESSAGE_ID=03bb1dab98ab4ecfbf6fff2738bdd964", 0);
|
||
}</programlisting>
|
||
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>See Also</title>
|
||
|
||
<para>
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</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_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|