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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>