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5aded36978
It is annoying when we have dead links on fd.o. Add project='man-pages|die-net|archlinux' to <citerefentry>-ies. In generated html, add external links to http://man7.org/linux/man-pages/man, http://linux.die.net/man/, https://www.archlinux.org/. By default, pages in sections 2 and 4 go to man7, since Michael Kerrisk is the autorative source on kernel related stuff. The rest of links goes to linux.die.net, because they have the manpages. Except for the pacman stuff, since it seems to be only available from archlinux.org. Poor gummiboot gets no link, because gummitboot(8) ain't to be found on the net. According to common wisdom, that would mean that it does not exist. But I have seen Kay using it, so I know it does, and deserves to be found. Can somebody be nice and put it up somewhere?
221 lines
11 KiB
XML
221 lines
11 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2012 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_journal_add_match">
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<refentryinfo>
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<title>sd_journal_add_match</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_journal_add_match</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_journal_add_match</refname>
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<refname>sd_journal_add_disjunction</refname>
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<refname>sd_journal_add_conjunction</refname>
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<refname>sd_journal_flush_matches</refname>
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<refpurpose>Add or remove entry matches</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_journal_add_match</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>const void *<parameter>data</parameter></paramdef>
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<paramdef>size_t <parameter>size</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_add_disjunction</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_add_conjunction</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_journal_flush_matches</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_journal_add_match()</function> adds
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a match by which to filter the entries of the journal
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file. Matches applied with this call will filter what
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can be iterated through and read from the journal file
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via calls like
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and
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<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Matches
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are of the form <literal>FIELD=value</literal>, where
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the field part is a short uppercase string consisting
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only of 0-9, A-Z and the underscore. It may not begin
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with two underscores or be the empty string. The value
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part may be any value, including binary. If a match is
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applied, only entries with this field set will be
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iterated. Multiple matches may be active at the same
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time: If they apply to different fields, only entries
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with both fields set like this will be iterated. If
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they apply to the same fields, only entries where the
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field takes one of the specified values will be
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iterated. Well known fields are documented in
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. Whenever
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a new match is added the current entry position is
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reset, and
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> (or a similar call)
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needs to be called before entries can be read
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again.</para>
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<para><function>sd_journal_add_disjunction()</function>
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may be used to insert a disjunction (i.e. logical OR)
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in the match list. If this call is invoked, all
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previously added matches since the last invocation of
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<function>sd_journal_add_disjunction()</function> or
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<function>sd_journal_add_conjunction()</function> are
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combined in an OR with all matches added afterwards,
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until
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<function>sd_journal_add_disjunction()</function> or
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<function>sd_journal_add_conjunction()</function> is
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invoked again to begin the next OR or AND
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term. </para>
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<para><function>sd_journal_add_conjunction()</function>
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may be used to insert a conjunction (i.e. logical AND)
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in the match list. If this call is invoked, all
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previously added matches since the last invocation of
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<function>sd_journal_add_conjunction()</function> are
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combined in an AND with all matches added afterwards,
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until
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<function>sd_journal_add_conjunction()</function> is
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invoked again to begin the next AND term. The
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combination of
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<function>sd_journal_add_match()</function>,
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<function>sd_journal_add_disjunction()</function> and
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<function>sd_journal_add_conjunction()</function> may
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be used to build complex search terms, even though
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full logical expressions are not available. Note that
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<function>sd_journal_add_conjunction()</function>
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operates one level 'higher' than
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<function>sd_journal_add_disjunction()</function>. It
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is hence possible to build an expression of AND terms,
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consisting of OR terms, consisting of AND terms,
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consisting of OR terms of matches (the latter OR
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expression is implicitly created for matches with the
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same field name, see above).</para>
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<para><function>sd_journal_flush_matches()</function>
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may be used to flush all matches, disjunction and
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conjunction terms again. After this call all filtering
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is removed and all entries in the journal will be
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iterated again.</para>
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<para>Note that filtering via matches only applies to
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the way the journal is read, it has no effect on storage
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on disk.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para><function>sd_journal_add_match()</function>,
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<function>sd_journal_add_disjunction()</function> and
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<function>sd_journal_add_conjunction()</function>
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return 0 on success or a negative errno-style error
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code. <function>sd_journal_flush_matches()</function>
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returns nothing.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>The <function>sd_journal_add_match()</function>,
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<function>sd_journal_add_disjunction()</function>,
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<function>sd_journal_add_conjunction()</function> and
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<function>sd_journal_flush_matches()</function>
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interfaces are available as a shared library, which can
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be compiled and linked to with the
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<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>The following example adds matches to a journal
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context object to iterate only through messages
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generated by the Avahi service at the four error log
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levels, plus all messages of the message ID
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03bb1dab98ab4ecfbf6fff2738bdd964 coming from any
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service (this example lacks the necessary error
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checking):</para>
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<programlisting>...
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int add_matches(sd_journal *j) {
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sd_journal_add_match(j, "_SYSTEMD_UNIT=avahi-daemon.service", 0);
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sd_journal_add_match(j, "PRIORITY=0", 0);
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sd_journal_add_match(j, "PRIORITY=1", 0);
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sd_journal_add_match(j, "PRIORITY=2", 0);
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sd_journal_add_match(j, "PRIORITY=3", 0);
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sd_journal_add_disjunction(j);
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sd_journal_add_match(j, "MESSAGE_ID=03bb1dab98ab4ecfbf6fff2738bdd964", 0);
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}</programlisting>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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