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3b3d7d069d
Shift the asterisks in the documentation's prototypes such that they are consistent among each other. Use the right side to match what is used in source code. Addendum to commit v209~82.
254 lines
13 KiB
XML
254 lines
13 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_open">
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<refentryinfo>
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<title>sd_journal_open</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_open</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_open</refname>
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<refname>sd_journal_open_directory</refname>
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<refname>sd_journal_open_files</refname>
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<refname>sd_journal_open_container</refname>
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<refname>sd_journal_close</refname>
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<refname>sd_journal</refname>
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<refname>SD_JOURNAL_LOCAL_ONLY</refname>
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<refname>SD_JOURNAL_RUNTIME_ONLY</refname>
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<refname>SD_JOURNAL_SYSTEM</refname>
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<refname>SD_JOURNAL_CURRENT_USER</refname>
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<refpurpose>Open the system journal for reading</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_open</function></funcdef>
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<paramdef>sd_journal **<parameter>ret</parameter></paramdef>
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<paramdef>int <parameter>flags</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_open_directory</function></funcdef>
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<paramdef>sd_journal **<parameter>ret</parameter></paramdef>
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<paramdef>const char *<parameter>path</parameter></paramdef>
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<paramdef>int <parameter>flags</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_open_files</function></funcdef>
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<paramdef>sd_journal **<parameter>ret</parameter></paramdef>
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<paramdef>const char **<parameter>paths</parameter></paramdef>
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<paramdef>int <parameter>flags</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_open_container</function></funcdef>
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<paramdef>sd_journal **<parameter>ret</parameter></paramdef>
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<paramdef>const char *<parameter>machine</parameter></paramdef>
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<paramdef>int <parameter>flags</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_journal_close</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_open()</function> opens
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the log journal for reading. It will find all journal
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files automatically and interleave them automatically
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when reading. As first argument it takes a pointer to
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a <varname>sd_journal</varname> pointer, which on
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success will contain a journal context object. The
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second argument is a flags field, which may consist of
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the following flags ORed together:
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<constant>SD_JOURNAL_LOCAL_ONLY</constant> makes sure
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only journal files generated on the local machine will
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be opened. <constant>SD_JOURNAL_RUNTIME_ONLY</constant>
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makes sure only volatile journal files will be opened,
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excluding those which are stored on persistent
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storage. <constant>SD_JOURNAL_SYSTEM</constant>
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will cause journal files of system services and the
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kernel (in opposition to user session processes) to
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be opened. <constant>SD_JOURNAL_CURRENT_USER</constant>
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will cause journal files of the current user to be
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opened. If neither <constant>SD_JOURNAL_SYSTEM</constant>
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nor <constant>SD_JOURNAL_CURRENT_USER</constant> are
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specified, all journal file types will be opened.</para>
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<para><function>sd_journal_open_directory()</function>
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is similar to <function>sd_journal_open()</function>
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but takes an absolute directory path as argument. All
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journal files in this directory will be opened and
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interleaved automatically. This call also takes a
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flags argument, but it must be passed as 0 as no flags
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are currently understood for this call.</para>
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<para><function>sd_journal_open_files()</function>
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is similar to <function>sd_journal_open()</function>
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but takes a <constant>NULL</constant>-terminated list
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of file paths to open. All files will be opened and
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interleaved automatically. This call also takes a
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flags argument, but it must be passed as 0 as no flags
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are currently understood for this call. Please note
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that in the case of a live journal, this function is only
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useful for debugging, because individual journal files
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can be rotated at any moment, and the opening of
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specific files is inherently racy.</para>
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<para><function>sd_journal_open_container()</function>
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is similar to <function>sd_journal_open()</function>
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but opens the journal files of a running
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OS container. The specified machine name refers to a
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container that is registered with
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<citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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<para><varname>sd_journal</varname> objects cannot be
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used in the child after a fork. Functions which take a
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journal object as an argument
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(<function>sd_journal_next()</function> and others)
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will return <constant>-ECHILD</constant> after a fork.
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</para>
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<para><function>sd_journal_close()</function> will
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close the journal context allocated with
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<function>sd_journal_open()</function> or
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<function>sd_journal_open_directory()</function> and
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free its resources.</para>
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<para>When opening the journal only journal files
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accessible to the calling user will be opened. If
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journal files are not accessible to the caller, this
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will be silently ignored.</para>
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<para>See
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for an example of how to iterate through the journal
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after opening it with
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<function>sd_journal_open()</function>.</para>
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<para>A journal context object returned by
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<function>sd_journal_open()</function> references a
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specific journal entry as <emphasis>current</emphasis> entry,
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similar to a file seek index in a classic file system
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file, but without absolute positions. It may be
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altered with
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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_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and related calls. The current entry position may be
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exported in <emphasis>cursor</emphasis> strings, as accessible
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via
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<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Cursor
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strings may be used to globally identify a specific
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journal entry in a stable way and then later to seek
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to it (or if the specific entry is not available
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locally, to its closest entry in time)
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<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>Notification of journal changes is available via
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<function>sd_journal_get_fd()</function> and related
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calls.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>The <function>sd_journal_open()</function>,
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<function>sd_journal_open_directory()</function>, and
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<function>sd_journal_open_files()</function> calls
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return 0 on success or a negative errno-style error
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code. <function>sd_journal_close()</function> returns
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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_open()</function>,
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<function>sd_journal_open_directory()</function> and
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<function>sd_journal_close()</function> interfaces are
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available as a shared library, which can be compiled and
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linked to with the
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<constant>libsystemd</constant> <citerefentry><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>History</title>
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<para><function>sd_journal_open()</function>,
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<function>sd_journal_close()</function>,
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<constant>SD_JOURNAL_LOCAL_ONLY</constant>,
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<constant>SD_JOURNAL_RUNTIME_ONLY</constant>,
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<constant>SD_JOURNAL_SYSTEM_ONLY</constant> were added
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in systemd-38.</para>
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<para><function>sd_journal_open_directory()</function>
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was added in systemd-187.</para>
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<para><constant>SD_JOURNAL_SYSTEM</constant>,
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<constant>SD_JOURNAL_CURRENT_USER</constant>,
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and <function>sd_journal_open_files()</function>
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were added in systemd-205.
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<constant>SD_JOURNAL_SYSTEM_ONLY</constant>
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was deprecated.</para>
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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_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-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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