man/sd_journal_print.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
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   8   Copyright 2012 Lennart Poettering
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  23
  24 <refentry id="sd_journal_print">
  25
  26         <refentryinfo>
  27                 <title>sd_journal_print</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_print</refentrytitle>
  42                 <manvolnum>3</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>sd_journal_print</refname>
  47                 <refname>sd_journal_printv</refname>
  48                 <refname>sd_journal_send</refname>
  49                 <refname>sd_journal_sendv</refname>
  50                 <refname>SD_JOURNAL_SUPPRESS_LOCATION</refname>
  51                 <refpurpose>Submit log entries to the journal</refpurpose>
  52         </refnamediv>
  53
  54         <refsynopsisdiv>
  55                 <funcsynopsis>
  56                         <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
  57
  58                         <funcprototype>
  59                                 <funcdef>int <function>sd_journal_print</function></funcdef>
  60                                 <paramdef>int <parameter>priority</parameter></paramdef>
  61                                 <paramdef>const char* <parameter>format</parameter></paramdef>
  62                                 <paramdef>...</paramdef>
  63                         </funcprototype>
  64
  65                         <funcprototype>
  66                                 <funcdef>int <function>sd_journal_printv</function></funcdef>
  67                                 <paramdef>int <parameter>priority</parameter></paramdef>
  68                                 <paramdef>const char* <parameter>format</parameter></paramdef>
  69                                 <paramdef>va_list <parameter>ap</parameter></paramdef>
  70                         </funcprototype>
  71
  72                         <funcprototype>
  73                                 <funcdef>int <function>sd_journal_send</function></funcdef>
  74                                 <paramdef>const char* <parameter>format</parameter></paramdef>
  75                                 <paramdef>...</paramdef>
  76                         </funcprototype>
  77
  78                         <funcprototype>
  79                                 <funcdef>int <function>sd_journal_sendv</function></funcdef>
  80                                 <paramdef>const struct iovec *<parameter>iov</parameter></paramdef>
  81                                 <paramdef>int <parameter>n</parameter></paramdef>
  82                         </funcprototype>
  83
  84                 </funcsynopsis>
  85         </refsynopsisdiv>
  86
  87         <refsect1>
  88                 <title>Description</title>
  89
  90                 <para><function>sd_journal_print()</function> may be
  91                 used to submit simple, plain text log entries to the
  92                 system journal. The first argument is a priority
  93                 value. This is followed by a format string and its
  94                 parameters, similar to
  95                 <citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  96                 or
  97                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
  98                 priority value is one of
  99                 <literal>LOG_EMERG</literal>,
 100                 <literal>LOG_ALERT</literal>,
 101                 <literal>LOG_CRIT</literal>,
 102                 <literal>LOG_ERR</literal>,
 103                 <literal>LOG_WARNING</literal>,
 104                 <literal>LOG_NOTICE</literal>,
 105                 <literal>LOG_INFO</literal>,
 106                 <literal>LOG_DEBUG</literal>, as defined in
 107                 <filename>syslog.h</filename>, see
 108                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 109                 for details. It is recommended to use this call to
 110                 submit log messages in the application locale or system
 111                 locale and in UTF-8 format, but no such restrictions
 112                 are enforced.</para>
 113
 114                 <para><function>sd_journal_printv()</function> is
 115                 similar to <function>sd_journal_print()</function> but
 116                 takes a variable argument list encapsulated in an
 117                 object of type <literal>va_list</literal> (see
 118                 <citerefentry><refentrytitle>stdarg</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 119                 for more information) instead of the format string. It
 120                 is otherwise equivalent in behaviour.</para>
 121
 122                 <para><function>sd_journal_send()</function> may be
 123                 used to submit structured log entries to the system
 124                 journal. It takes a series of format strings, each
 125                 immediately followed by their associated parameters,
 126                 terminated by NULL. The strings passed should be of
 127                 the format <literal>VARIABLE=value</literal>. The
 128                 variable name must be in uppercase and consist only
 129                 of characters, numbers and underscores, and may not
 130                 begin with an underscore. The value can be of any size
 131                 and format. It is highly recommended to submit
 132                 text strings formatted in the UTF-8 character encoding
 133                 only, and submit binary fields only when formatting in
 134                 UTf-8 strings is not sensible. A number of well known
 135                 fields are defined, see
 136                 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 137                 for details, but additional application defined fields
 138                 may be used.</para>
 139
 140                 <para><function>sd_journal_sendv()</function> is
 141                 similar to <function>sd_journal_send()</function> but
 142                 takes an array of <literal>struct iovec</literal> (as
 143                 defined in <filename>uio.h</filename>, see
 144                 <citerefentry><refentrytitle>readv</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 145                 for details) instead of the format string. Each
 146                 structure should reference one field of the entry to
 147                 submit. The second argument specifies the number of
 148                 structures in the
 149                 array. <function>sd_journal_sendv()</function> is
 150                 particularly useful to submit binary objects to the
 151                 journal where that is necessary.</para>
 152
 153                 <para>Note that <function>sd_journal_send()</function>
 154                 is a wrapper around
 155                 <function>sd_journal_sendv()</function> to make it
 156                 easier to use when only text strings shall be
 157                 submitted. Also, the following two calls are
 158                 mostly equivalent:</para>
 159
 160                 <programlisting>sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid());
 161
 162 sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(),
 163                 "PRIORITY=%i", LOG_INFO,
 164                 NULL);</programlisting>
 165
 166                 <para>Note that these calls implicitly add fields for
 167                 the source file, function name and code line where
 168                 invoked. This is implemented with macros. If this is
 169                 not desired it can be turned off by defining
 170                 SD_JOURNAL_SUPPRESS_LOCATION before including
 171                 <filename>sd-journal.h</filename>.</para>
 172
 173                 <para><citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 174                 and and <function>sd_journal_print()</function> may
 175                 largely be used interchangeably
 176                 functionality-wise. However, note that log messages
 177                 logged via the former take a different path to the
 178                 journal server than the later, and hence global
 179                 chronological ordering between the two streams cannot
 180                 be guaranteed. Using
 181                 <function>sd_journal_print()</function> has the
 182                 benefit of logging source code line, file names, and
 183                 functions as meta data along all entries, and
 184                 guaranteeing chronological ordering with structured
 185                 log entries that are generated via
 186                 <function>sd_journal_send()</function>. Using
 187                 <function>syslog()</function> has the benefit of being
 188                 more portable.</para>
 189         </refsect1>
 190
 191         <refsect1>
 192                 <title>Return Value</title>
 193
 194                 <para>The four calls return 0 on success or a
 195                 negative errno-style error code.</para>
 196         </refsect1>
 197
 198         <refsect1>
 199                 <title>Notes</title>
 200
 201                 <para>The <function>sd_journal_print()</function>,
 202                 <function>sd_journal_printv()</function>,
 203                 <function>sd_journal_send()</function> and
 204                 <function>sd_journal_sendv()</function> interfaces
 205                 are available as shared library, which can be compiled
 206                 and linked to with the
 207                 <literal>libsystemd-journal</literal>
 208                 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 209                 file.</para>
 210         </refsect1>
 211
 212         <refsect1>
 213                 <title>See Also</title>
 214
 215                 <para>
 216                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 217                         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 218                         <citerefentry><refentrytitle>sd_journal_stream_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 219                         <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 220                         <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 221                 </para>
 222         </refsect1>
 223
 224 </refentry>