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 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>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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