<?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_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>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><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-journal</constant> <citerefentry><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> </para> </refsect1> </refentry>