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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_files</refname>
<refname>sd_journal_open_container</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>
<refpurpose>Open the system journal for reading</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-journal.h></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_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_container</function></funcdef>
<paramdef>sd_journal **<parameter>ret</parameter></paramdef>
<paramdef>const char *<parameter>machine</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, but it must be passed as 0 as no flags are
currently understood for this call.</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_container()</function> is similar
to <function>sd_journal_open()</function> but opens the journal
files of a running OS container. The specified machine name refers
to a container that is registered with
<citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</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>History</title>
<para><function>sd_journal_open()</function>,
<function>sd_journal_close()</function>,
<constant>SD_JOURNAL_LOCAL_ONLY</constant>,
<constant>SD_JOURNAL_RUNTIME_ONLY</constant>,
<constant>SD_JOURNAL_SYSTEM_ONLY</constant> were added in
systemd-38.</para>
<para><function>sd_journal_open_directory()</function> was added
in systemd-187.</para>
<para><constant>SD_JOURNAL_SYSTEM</constant>,
<constant>SD_JOURNAL_CURRENT_USER</constant>, and
<function>sd_journal_open_files()</function> were added in
systemd-205. <constant>SD_JOURNAL_SYSTEM_ONLY</constant> was
deprecated.</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>
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