man/sd_journal_open.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2012 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="sd_journal_open">
  25
  26         <refentryinfo>
  27                 <title>sd_journal_open</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>sd_journal_open</refentrytitle>
  42                 <manvolnum>3</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>sd_journal_open</refname>
  47                 <refname>sd_journal_open_directory</refname>
  48                 <refname>sd_journal_close</refname>
  49                 <refname>sd_journal</refname>
  50                 <refname>SD_JOURNAL_LOCAL_ONLY</refname>
  51                 <refname>SD_JOURNAL_RUNTIME_ONLY</refname>
  52                 <refname>SD_JOURNAL_SYSTEM</refname>
  53                 <refname>SD_JOURNAL_CURRENT_USER</refname>
  54                 <refpurpose>Open the system journal for reading</refpurpose>
  55         </refnamediv>
  56
  57         <refsynopsisdiv>
  58                 <funcsynopsis>
  59                         <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
  60
  61                         <funcprototype>
  62                                 <funcdef>int <function>sd_journal_open</function></funcdef>
  63                                 <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
  64                                 <paramdef>int <parameter>flags</parameter></paramdef>
  65                         </funcprototype>
  66
  67                         <funcprototype>
  68                                 <funcdef>int <function>sd_journal_open_directory</function></funcdef>
  69                                 <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
  70                                 <paramdef>const char* <parameter>path</parameter></paramdef>
  71                                 <paramdef>int <parameter>flags</parameter></paramdef>
  72                         </funcprototype>
  73
  74                         <funcprototype>
  75                                 <funcdef>void <function>sd_journal_close</function></funcdef>
  76                                 <paramdef>sd_journal* <parameter>j</parameter></paramdef>
  77                         </funcprototype>
  78                 </funcsynopsis>
  79         </refsynopsisdiv>
  80
  81         <refsect1>
  82                 <title>Description</title>
  83
  84                 <para><function>sd_journal_open()</function> opens
  85                 the log journal for reading. It will find all journal
  86                 files automatically and interleave them automatically
  87                 when reading. As first argument it takes a pointer to
  88                 a <literal>sd_journal</literal> pointer, which on
  89                 success will contain journal context object afterwards. The
  90                 second argument is a flags field, which may consist of
  91                 the following flags ORed together:
  92                 <literal>SD_JOURNAL_LOCAL_ONLY</literal> makes sure
  93                 only journal files generated on the local machine will
  94                 be opened. <literal>SD_JOURNAL_RUNTIME_ONLY</literal>
  95                 makes sure only volatile journal files will be opened,
  96                 excluding those which are stored on persistent
  97                 storage. <literal>SD_JOURNAL_SYSTEM</literal>
  98                 will cause journal files of system services and the
  99                 kernel (in opposition to user session processes) to
 100                 be opened. <literal>SD_JOURNAL_CURRENT_USER</literal>
 101                 will cause journal files of the current user to be
 102                 opened. If neither <literal>SD_JOURNAL_SYSTEM</literal>
 103                 nor <literal>SD_JOURNAL_CURRENT_USER</literal> are
 104                 specified, all journal file types will be opened.</para>
 105
 106                 <para><function>sd_journal_open_directory()</function>
 107                 is similar to <function>sd_journal_open()</function>
 108                 but takes an absolute directory path as argument. All
 109                 journal files in this directory will be opened and
 110                 interleaved automatically. This call also takes a
 111                 flags argument, but it must be passed as 0 as no flags
 112                 are currently understood for this call.</para>
 113
 114                 <para><function>sd_journal_close()</function> will
 115                 close the journal context allocated with
 116                 <function>sd_journal_open()</function> or
 117                 <function>sd_journal_open_directory()</function> and
 118                 free its resources.</para>
 119
 120                 <para>When opening the journal only journal files
 121                 accessible to the calling user will be opened. If
 122                 journal files are not accessible to the caller this
 123                 will be silently ignored.</para>
 124
 125                 <para>See
 126                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 127                 for an example how to iterate through the journal
 128                 after opening it with
 129                 <function>sd_journal_open()</function>.</para>
 130
 131                 <para>A journal context object returned by
 132                 <function>sd_journal_open()</function> references a
 133                 specific journal entry as <emphasis>current</emphasis> entry,
 134                 similar to a file seek index in a classic file system
 135                 file, but without absolute positions. It may be
 136                 altered with
 137                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 138                 and
 139                 <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 140                 and related calls. The current entry position may be
 141                 exported in <emphasis>cursor</emphasis> strings, as accessible
 142                 via
 143                 <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Cursor
 144                 strings may be used to globally identify a specific
 145                 journal entry in a stable way and then later to seek
 146                 to it (or if the specific entry is not available
 147                 locally, to its closest entry in time)
 148                 <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 149
 150                 <para>Notification of journal changes is available via
 151                 <function>sd_journal_get_fd()</function> and related
 152                 calls.</para>
 153         </refsect1>
 154
 155         <refsect1>
 156                 <title>Return Value</title>
 157
 158                 <para>The <function>sd_journal_open()</function> and
 159                 <function>sd_journal_open_directory()</function> calls
 160                 return 0 on success or a negative errno-style error
 161                 code. <function>sd_journal_close()</function> returns
 162                 nothing.</para>
 163         </refsect1>
 164
 165         <refsect1>
 166                 <title>Notes</title>
 167
 168                 <para>The <function>sd_journal_open()</function>,
 169                 <function>sd_journal_open_directory()</function> and
 170                 <function>sd_journal_close()</function> interfaces are
 171                 available as shared library, which can be compiled and
 172                 linked to with the
 173                 <literal>libsystemd-journal</literal>
 174                 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 175                 file.</para>
 176         </refsect1>
 177
 178         <refsect1>
 179                 <title>History</title>
 180
 181                 <para><function>sd_journal_open()</function>,
 182                 <function>sd_journal_close()</function>,
 183                 <literal>SD_JOURNAL_LOCAL_ONLY</literal>,
 184                 <literal>SD_JOURNAL_RUNTIME_ONLY</literal>,
 185                 <literal>SD_JOURNAL_SYSTEM_ONLY</literal> were added
 186                 in systemd-38.</para>
 187
 188                 <para><function>sd_journal_open_directory()</function>
 189                 was added in systemd-187.</para>
 190
 191                 <para><literal>SD_JOURNAL_SYSTEM</literal> and
 192                 <literal>SD_JOURNAL_CURRENT_USER</literal> were added
 193                 in systemd-205.
 194                 <literal>SD_JOURNAL_SYSTEM_ONLY</literal>
 195                 was deprecated.</para>
 196         </refsect1>
 197
 198         <refsect1>
 199                 <title>See Also</title>
 200
 201                 <para>
 202                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 203                         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 204                         <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 205                         <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 206                 </para>
 207         </refsect1>
 208
 209 </refentry>