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">
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   8   Copyright 2012 Lennart Poettering
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  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_open_files</refname>
  49                 <refname>sd_journal_close</refname>
  50                 <refname>sd_journal</refname>
  51                 <refname>SD_JOURNAL_LOCAL_ONLY</refname>
  52                 <refname>SD_JOURNAL_RUNTIME_ONLY</refname>
  53                 <refname>SD_JOURNAL_SYSTEM</refname>
  54                 <refname>SD_JOURNAL_CURRENT_USER</refname>
  55                 <refpurpose>Open the system journal for reading</refpurpose>
  56         </refnamediv>
  57
  58         <refsynopsisdiv>
  59                 <funcsynopsis>
  60                         <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
  61
  62                         <funcprototype>
  63                                 <funcdef>int <function>sd_journal_open</function></funcdef>
  64                                 <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
  65                                 <paramdef>int <parameter>flags</parameter></paramdef>
  66                         </funcprototype>
  67
  68                         <funcprototype>
  69                                 <funcdef>int <function>sd_journal_open_directory</function></funcdef>
  70                                 <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
  71                                 <paramdef>const char* <parameter>path</parameter></paramdef>
  72                                 <paramdef>int <parameter>flags</parameter></paramdef>
  73                         </funcprototype>
  74
  75                         <funcprototype>
  76                                 <funcdef>int <function>sd_journal_open_files</function></funcdef>
  77                                 <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
  78                                 <paramdef>const char** <parameter>paths</parameter></paramdef>
  79                                 <paramdef>int <parameter>flags</parameter></paramdef>
  80                         </funcprototype>
  81
  82                         <funcprototype>
  83                                 <funcdef>void <function>sd_journal_close</function></funcdef>
  84                                 <paramdef>sd_journal* <parameter>j</parameter></paramdef>
  85                         </funcprototype>
  86                 </funcsynopsis>
  87         </refsynopsisdiv>
  88
  89         <refsect1>
  90                 <title>Description</title>
  91
  92                 <para><function>sd_journal_open()</function> opens
  93                 the log journal for reading. It will find all journal
  94                 files automatically and interleave them automatically
  95                 when reading. As first argument it takes a pointer to
  96                 a <literal>sd_journal</literal> pointer, which on
  97                 success will contain journal context object afterwards. The
  98                 second argument is a flags field, which may consist of
  99                 the following flags ORed together:
 100                 <literal>SD_JOURNAL_LOCAL_ONLY</literal> makes sure
 101                 only journal files generated on the local machine will
 102                 be opened. <literal>SD_JOURNAL_RUNTIME_ONLY</literal>
 103                 makes sure only volatile journal files will be opened,
 104                 excluding those which are stored on persistent
 105                 storage. <literal>SD_JOURNAL_SYSTEM</literal>
 106                 will cause journal files of system services and the
 107                 kernel (in opposition to user session processes) to
 108                 be opened. <literal>SD_JOURNAL_CURRENT_USER</literal>
 109                 will cause journal files of the current user to be
 110                 opened. If neither <literal>SD_JOURNAL_SYSTEM</literal>
 111                 nor <literal>SD_JOURNAL_CURRENT_USER</literal> are
 112                 specified, all journal file types will be opened.</para>
 113
 114                 <para><function>sd_journal_open_directory()</function>
 115                 is similar to <function>sd_journal_open()</function>
 116                 but takes an absolute directory path as argument. All
 117                 journal files in this directory will be opened and
 118                 interleaved automatically. This call also takes a
 119                 flags argument, but it must be passed as 0 as no flags
 120                 are currently understood for this call.</para>
 121
 122                 <para><function>sd_journal_open_files()</function>
 123                 is similar to <function>sd_journal_open()</function>
 124                 but takes a <literal>NULL</literal>-terminated list
 125                 of file paths to open. All files will be opened and
 126                 interleaved automatically. This call also takes a
 127                 flags argument, but it must be passed as 0 as no flags
 128                 are currently understood for this call.</para>
 129
 130                 <para><function>sd_journal_close()</function> will
 131                 close the journal context allocated with
 132                 <function>sd_journal_open()</function> or
 133                 <function>sd_journal_open_directory()</function> and
 134                 free its resources.</para>
 135
 136                 <para>When opening the journal only journal files
 137                 accessible to the calling user will be opened. If
 138                 journal files are not accessible to the caller this
 139                 will be silently ignored.</para>
 140
 141                 <para>See
 142                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 143                 for an example how to iterate through the journal
 144                 after opening it with
 145                 <function>sd_journal_open()</function>.</para>
 146
 147                 <para>A journal context object returned by
 148                 <function>sd_journal_open()</function> references a
 149                 specific journal entry as <emphasis>current</emphasis> entry,
 150                 similar to a file seek index in a classic file system
 151                 file, but without absolute positions. It may be
 152                 altered with
 153                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 154                 and
 155                 <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 156                 and related calls. The current entry position may be
 157                 exported in <emphasis>cursor</emphasis> strings, as accessible
 158                 via
 159                 <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Cursor
 160                 strings may be used to globally identify a specific
 161                 journal entry in a stable way and then later to seek
 162                 to it (or if the specific entry is not available
 163                 locally, to its closest entry in time)
 164                 <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 165
 166                 <para>Notification of journal changes is available via
 167                 <function>sd_journal_get_fd()</function> and related
 168                 calls.</para>
 169         </refsect1>
 170
 171         <refsect1>
 172                 <title>Return Value</title>
 173
 174                 <para>The <function>sd_journal_open()</function> and
 175                 <function>sd_journal_open_directory()</function> calls
 176                 return 0 on success or a negative errno-style error
 177                 code. <function>sd_journal_close()</function> returns
 178                 nothing.</para>
 179         </refsect1>
 180
 181         <refsect1>
 182                 <title>Notes</title>
 183
 184                 <para>The <function>sd_journal_open()</function>,
 185                 <function>sd_journal_open_directory()</function> and
 186                 <function>sd_journal_close()</function> interfaces are
 187                 available as shared library, which can be compiled and
 188                 linked to with the
 189                 <literal>libsystemd-journal</literal>
 190                 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 191                 file.</para>
 192         </refsect1>
 193
 194         <refsect1>
 195                 <title>History</title>
 196
 197                 <para><function>sd_journal_open()</function>,
 198                 <function>sd_journal_close()</function>,
 199                 <literal>SD_JOURNAL_LOCAL_ONLY</literal>,
 200                 <literal>SD_JOURNAL_RUNTIME_ONLY</literal>,
 201                 <literal>SD_JOURNAL_SYSTEM_ONLY</literal> were added
 202                 in systemd-38.</para>
 203
 204                 <para><function>sd_journal_open_directory()</function>
 205                 was added in systemd-187.</para>
 206
 207                 <para><literal>SD_JOURNAL_SYSTEM</literal>,
 208                 <literal>SD_JOURNAL_CURRENT_USER</literal>,
 209                 and <function>sd_journal_open_files()</function>
 210                 were added in systemd-205.
 211                 <literal>SD_JOURNAL_SYSTEM_ONLY</literal>
 212                 was deprecated.</para>
 213         </refsect1>
 214
 215         <refsect1>
 216                 <title>See Also</title>
 217
 218                 <para>
 219                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 220                         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 221                         <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 222                         <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 223                 </para>
 224         </refsect1>
 225
 226 </refentry>