mirror of
https://github.com/systemd/systemd.git
synced 2024-12-17 06:03:35 +08:00
254 lines
13 KiB
XML
254 lines
13 KiB
XML
<?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><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>
|