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+<?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_open">
+
+ <refentryinfo>
+ <title>sd_journal_open</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_open</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_journal_open</refname>
+ <refname>sd_journal_open_directory</refname>
+ <refname>sd_journal_open_directory_fd</refname>
+ <refname>sd_journal_open_files</refname>
+ <refname>sd_journal_open_files_fd</refname>
+ <refname>sd_journal_close</refname>
+ <refname>sd_journal</refname>
+ <refname>SD_JOURNAL_LOCAL_ONLY</refname>
+ <refname>SD_JOURNAL_RUNTIME_ONLY</refname>
+ <refname>SD_JOURNAL_SYSTEM</refname>
+ <refname>SD_JOURNAL_CURRENT_USER</refname>
+ <refname>SD_JOURNAL_OS_ROOT</refname>
+ <refpurpose>Open the system journal for reading</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_open</function></funcdef>
+ <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_open_directory</function></funcdef>
+ <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
+ <paramdef>const char *<parameter>path</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_open_directory_fd</function></funcdef>
+ <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_open_files</function></funcdef>
+ <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
+ <paramdef>const char **<parameter>paths</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_open_files_fd</function></funcdef>
+ <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
+ <paramdef>int <parameter>fds[]</parameter></paramdef>
+ <paramdef>unsigned <parameter>n_fds</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>void <function>sd_journal_close</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_journal_open()</function> opens the log journal
+ for reading. It will find all journal files automatically and
+ interleave them automatically when reading. As first argument it
+ takes a pointer to a <varname>sd_journal</varname> pointer, which,
+ on success, will contain a journal context object. The second
+ argument is a flags field, which may consist of the following
+ flags ORed together: <constant>SD_JOURNAL_LOCAL_ONLY</constant>
+ makes sure only journal files generated on the local machine will
+ be opened. <constant>SD_JOURNAL_RUNTIME_ONLY</constant> makes sure
+ only volatile journal files will be opened, excluding those which
+ are stored on persistent storage.
+ <constant>SD_JOURNAL_SYSTEM</constant> will cause journal files of
+ system services and the kernel (in opposition to user session
+ processes) to be opened.
+ <constant>SD_JOURNAL_CURRENT_USER</constant> will cause journal
+ files of the current user to be opened. If neither
+ <constant>SD_JOURNAL_SYSTEM</constant> nor
+ <constant>SD_JOURNAL_CURRENT_USER</constant> are specified, all
+ journal file types will be opened.</para>
+
+ <para><function>sd_journal_open_directory()</function> is similar to <function>sd_journal_open()</function> but
+ takes an absolute directory path as argument. All journal files in this directory will be opened and interleaved
+ automatically. This call also takes a flags argument. The only flags parameter accepted by this call is
+ <constant>SD_JOURNAL_OS_ROOT</constant>. If specified, the journal files are searched below the usual
+ <filename>/var/log/journal</filename> and <filename>/run/log/journal</filename> relative to the specified path,
+ instead of directly beneath it.</para>
+
+ <para><function>sd_journal_open_directory_fd()</function> is similar to
+ <function>sd_journal_open_directory()</function>, but takes a file descriptor referencing a directory in the file
+ system instead of an absolute file system path.</para>
+
+ <para><function>sd_journal_open_files()</function> is similar to <function>sd_journal_open()</function> but takes a
+ <constant>NULL</constant>-terminated list of file paths to open. All files will be opened and interleaved
+ automatically. This call also takes a flags argument, but it must be passed as 0 as no flags are currently
+ understood for this call. Please note that in the case of a live journal, this function is only useful for
+ debugging, because individual journal files can be rotated at any moment, and the opening of specific files is
+ inherently racy.</para>
+
+ <para><function>sd_journal_open_files_fd()</function> is similar to <function>sd_journal_open_files()</function>
+ but takes an array of open file descriptors that must reference journal files, instead of an array of file system
+ paths. Pass the array of file descriptors as second argument, and the number of array entries in the third. The
+ flags parameter must be passed as 0.</para>
+
+ <para><varname>sd_journal</varname> objects cannot be used in the
+ child after a fork. Functions which take a journal object as an
+ argument (<function>sd_journal_next()</function> and others) will
+ return <constant>-ECHILD</constant> after a fork.
+ </para>
+
+ <para><function>sd_journal_close()</function> will close the
+ journal context allocated with
+ <function>sd_journal_open()</function> or
+ <function>sd_journal_open_directory()</function> and free its
+ resources.</para>
+
+ <para>When opening the journal only journal files accessible to
+ the calling user will be opened. If journal files are not
+ accessible to the caller, this will be silently ignored.</para>
+
+ <para>See
+ <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for an example of how to iterate through the journal after opening
+ it with <function>sd_journal_open()</function>.</para>
+
+ <para>A journal context object returned by
+ <function>sd_journal_open()</function> references a specific
+ journal entry as <emphasis>current</emphasis> entry, similar to a
+ file seek index in a classic file system file, but without
+ absolute positions. It may be altered with
+ <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ and
+ <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ and related calls. The current entry position may be exported in
+ <emphasis>cursor</emphasis> strings, as accessible via
+ <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ Cursor strings may be used to globally identify a specific journal
+ entry in a stable way and then later to seek to it (or if the
+ specific entry is not available locally, to its closest entry in
+ time)
+ <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+ <para>Notification of journal changes is available via
+ <function>sd_journal_get_fd()</function> and related calls.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>The <function>sd_journal_open()</function>,
+ <function>sd_journal_open_directory()</function>, and
+ <function>sd_journal_open_files()</function> calls return 0 on
+ success or a negative errno-style error code.
+ <function>sd_journal_close()</function> returns nothing.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>The <function>sd_journal_open()</function>,
+ <function>sd_journal_open_directory()</function> and
+ <function>sd_journal_close()</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>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_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>