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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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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_print"> | |
25 | ||
798d3a52 ZJS |
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_perror</refname> | |
51 | <refname>SD_JOURNAL_SUPPRESS_LOCATION</refname> | |
52 | <refpurpose>Submit log entries to the journal</refpurpose> | |
53 | </refnamediv> | |
54 | ||
55 | <refsynopsisdiv> | |
56 | <funcsynopsis> | |
57 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
58 | ||
59 | <funcprototype> | |
60 | <funcdef>int <function>sd_journal_print</function></funcdef> | |
61 | <paramdef>int <parameter>priority</parameter></paramdef> | |
62 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 63 | <paramdef>…</paramdef> |
798d3a52 ZJS |
64 | </funcprototype> |
65 | ||
66 | <funcprototype> | |
67 | <funcdef>int <function>sd_journal_printv</function></funcdef> | |
68 | <paramdef>int <parameter>priority</parameter></paramdef> | |
69 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
70 | <paramdef>va_list <parameter>ap</parameter></paramdef> | |
71 | </funcprototype> | |
72 | ||
73 | <funcprototype> | |
74 | <funcdef>int <function>sd_journal_send</function></funcdef> | |
75 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 76 | <paramdef>…</paramdef> |
798d3a52 ZJS |
77 | </funcprototype> |
78 | ||
79 | <funcprototype> | |
80 | <funcdef>int <function>sd_journal_sendv</function></funcdef> | |
81 | <paramdef>const struct iovec *<parameter>iov</parameter></paramdef> | |
82 | <paramdef>int <parameter>n</parameter></paramdef> | |
83 | </funcprototype> | |
84 | ||
85 | <funcprototype> | |
86 | <funcdef>int <function>sd_journal_perror</function></funcdef> | |
87 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
88 | </funcprototype> | |
89 | ||
90 | </funcsynopsis> | |
91 | </refsynopsisdiv> | |
92 | ||
93 | <refsect1> | |
94 | <title>Description</title> | |
95 | ||
4c5db93f LP |
96 | <para><function>sd_journal_print()</function> may be used to submit simple, plain text log entries to the system |
97 | journal. The first argument is a priority value. This is followed by a format string and its parameters, similar to | |
98 | <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> or | |
798d3a52 | 99 | <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
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100 | The priority value is one of <constant>LOG_EMERG</constant>, <constant>LOG_ALERT</constant>, |
101 | <constant>LOG_CRIT</constant>, <constant>LOG_ERR</constant>, <constant>LOG_WARNING</constant>, | |
102 | <constant>LOG_NOTICE</constant>, <constant>LOG_INFO</constant>, <constant>LOG_DEBUG</constant>, as defined in | |
103 | <filename>syslog.h</filename>, see <citerefentry | |
104 | project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> for details. It is | |
105 | recommended to use this call to submit log messages in the application locale or system locale and in UTF-8 format, | |
106 | but no such restrictions are enforced. Note that log messages written using this function are generally not | |
107 | expected to end in a new-line character. However, as all trailing whitespace (including spaces, new-lines, | |
108 | tabulators and carriage returns) are automatically stripped from the logged string, it is acceptable to specify one | |
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109 | (or more). Empty lines (after trailing whitespace removal) are suppressed. On non-empty lines, leading whitespace |
110 | (as well as inner whitespace) is left unmodified. </para> | |
798d3a52 ZJS |
111 | |
112 | <para><function>sd_journal_printv()</function> is similar to | |
113 | <function>sd_journal_print()</function> but takes a variable | |
114 | argument list encapsulated in an object of type | |
115 | <varname>va_list</varname> (see | |
3ba3a79d | 116 | <citerefentry project='man-pages'><refentrytitle>stdarg</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
798d3a52 ZJS |
117 | for more information) instead of the format string. It is |
118 | otherwise equivalent in behavior.</para> | |
119 | ||
4c5db93f LP |
120 | <para><function>sd_journal_send()</function> may be used to submit structured log entries to the system journal. It |
121 | takes a series of format strings, each immediately followed by their associated parameters, terminated by | |
122 | <constant>NULL</constant>. The strings passed should be of the format <literal>VARIABLE=value</literal>. The | |
123 | variable name must be in uppercase and consist only of characters, numbers and underscores, and may not begin with | |
124 | an underscore. (All assignments that do not follow this syntax will be ignored.) The value can be of any size and | |
125 | format. It is highly recommended to submit text strings formatted in the UTF-8 character encoding only, and submit | |
126 | binary fields only when formatting in UTF-8 strings is not sensible. A number of well-known fields are defined, see | |
127 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> for | |
128 | details, but additional application defined fields may be used. A variable may be assigned more than one value per | |
129 | entry. If this function is used, trailing whitespace is automatically removed from each formatted field.</para> | |
130 | ||
131 | <para><function>sd_journal_sendv()</function> is similar to <function>sd_journal_send()</function> but takes an | |
132 | array of <varname>struct iovec</varname> (as defined in <filename>uio.h</filename>, see <citerefentry | |
133 | project='man-pages'><refentrytitle>readv</refentrytitle><manvolnum>3</manvolnum></citerefentry> for details) | |
134 | instead of the format string. Each structure should reference one field of the entry to submit. The second argument | |
135 | specifies the number of structures in the array. <function>sd_journal_sendv()</function> is particularly useful to | |
301a21a8 | 136 | submit binary objects to the journal where that is necessary. Note that this function will not strip trailing |
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137 | whitespace of the passed fields, but passes the specified data along unmodified. This is different from both |
138 | <function>sd_journal_print()</function> and <function>sd_journal_send()</function> described above, which are based | |
139 | on format strings, and do strip trailing whitespace.</para> | |
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140 | |
141 | <para><function>sd_journal_perror()</function> is a similar to | |
3ba3a79d | 142 | <citerefentry project='die-net'><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
798d3a52 | 143 | and writes a message to the journal that consists of the passed |
b938cb90 | 144 | string, suffixed with ": " and a human-readable representation of |
798d3a52 ZJS |
145 | the current error code stored in |
146 | <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
147 | If the message string is passed as <constant>NULL</constant> or | |
148 | empty string, only the error string representation will be | |
149 | written, prefixed with nothing. An additional journal field ERRNO= | |
150 | is included in the entry containing the numeric error code | |
151 | formatted as decimal string. The log priority used is | |
152 | <constant>LOG_ERR</constant> (3).</para> | |
153 | ||
154 | <para>Note that <function>sd_journal_send()</function> is a | |
155 | wrapper around <function>sd_journal_sendv()</function> to make it | |
156 | easier to use when only text strings shall be submitted. Also, the | |
157 | following two calls are mostly equivalent:</para> | |
158 | ||
159 | <programlisting>sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid()); | |
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160 | |
161 | sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(), | |
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162 | "PRIORITY=%i", LOG_INFO, |
163 | NULL);</programlisting> | |
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164 | |
165 | <para>Note that these calls implicitly add fields for the source | |
166 | file, function name and code line where invoked. This is | |
167 | implemented with macros. If this is not desired, it can be turned | |
168 | off by defining SD_JOURNAL_SUPPRESS_LOCATION before including | |
169 | <filename>sd-journal.h</filename>.</para> | |
170 | ||
171 | <para><citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
172 | and <function>sd_journal_print()</function> may | |
173 | largely be used interchangeably | |
174 | functionality-wise. However, note that log messages | |
175 | logged via the former take a different path to the | |
176 | journal server than the later, and hence global | |
177 | chronological ordering between the two streams cannot | |
178 | be guaranteed. Using | |
179 | <function>sd_journal_print()</function> has the | |
180 | benefit of logging source code line, filenames, and | |
181 | functions as metadata along all entries, and | |
182 | guaranteeing chronological ordering with structured | |
183 | log entries that are generated via | |
184 | <function>sd_journal_send()</function>. Using | |
185 | <function>syslog()</function> has the benefit of being | |
186 | more portable.</para> | |
187 | </refsect1> | |
188 | ||
189 | <refsect1> | |
190 | <title>Return Value</title> | |
191 | ||
951aba62 LP |
192 | <para>The five calls return 0 on success or a negative errno-style error code. The <citerefentry |
193 | project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry> variable itself is | |
194 | not altered.</para> | |
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195 | |
196 | <para>If | |
197 | <citerefentry><refentrytitle>systemd-journald</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
198 | is not running (the socket is not present), those functions do | |
199 | nothing, and also return 0.</para> | |
200 | </refsect1> | |
201 | ||
202 | <refsect1> | |
a8d46a16 ZJS |
203 | <title>Thread safety</title> |
204 | <para>All functions listed here are thread-safe and may be called in parallel from multiple threads.</para> | |
205 | ||
206 | <para><function>sd_journal_sendv()</function> is "async signal safe" in the meaning of | |
3ba3a79d | 207 | <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>. |
798d3a52 ZJS |
208 | </para> |
209 | ||
210 | <para><function>sd_journal_print</function>, | |
211 | <function>sd_journal_printv</function>, | |
212 | <function>sd_journal_send</function>, and | |
213 | <function>sd_journal_perror</function> are | |
214 | not async signal safe.</para> | |
215 | </refsect1> | |
216 | ||
217 | <refsect1> | |
218 | <title>Notes</title> | |
219 | ||
951aba62 LP |
220 | <para>The <function>sd_journal_print()</function>, <function>sd_journal_printv()</function>, |
221 | <function>sd_journal_send()</function>, <function>sd_journal_sendv()</function> and | |
222 | <function>sd_journal_perror()</function> interfaces are available as a shared library, which can be compiled and | |
223 | linked to with the <constant>libsystemd</constant> <citerefentry | |
224 | project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> | |
798d3a52 ZJS |
225 | </refsect1> |
226 | ||
227 | <refsect1> | |
228 | <title>See Also</title> | |
229 | ||
230 | <para> | |
231 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
232 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
233 | <citerefentry><refentrytitle>sd_journal_stream_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
234 | <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
3ba3a79d | 235 | <citerefentry project='die-net'><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
798d3a52 ZJS |
236 | <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
237 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
3ba3a79d ZJS |
238 | <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>, |
239 | <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
798d3a52 ZJS |
240 | </para> |
241 | </refsect1> | |
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242 | |
243 | </refentry> |