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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 | <!-- | |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
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8 | This file is part of systemd. |
9 | ||
10 | Copyright 2012 Lennart Poettering | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
26 | <refentry id="sd_journal_stream_fd"> | |
27 | ||
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28 | <refentryinfo> |
29 | <title>sd_journal_stream_fd</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>Developer</contrib> | |
35 | <firstname>Lennart</firstname> | |
36 | <surname>Poettering</surname> | |
37 | <email>lennart@poettering.net</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_journal_stream_fd</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_journal_stream_fd</refname> | |
49 | <refpurpose>Create log stream file descriptor to the journal</refpurpose> | |
50 | </refnamediv> | |
51 | ||
52 | <refsynopsisdiv> | |
53 | <funcsynopsis> | |
54 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
55 | ||
56 | <funcprototype> | |
57 | <funcdef>int <function>sd_journal_stream_fd</function></funcdef> | |
58 | <paramdef>const char *<parameter>identifier</parameter></paramdef> | |
59 | <paramdef>int <parameter>priority</parameter></paramdef> | |
60 | <paramdef>int <parameter>level_prefix</parameter></paramdef> | |
61 | </funcprototype> | |
62 | ||
63 | </funcsynopsis> | |
64 | </refsynopsisdiv> | |
65 | ||
66 | <refsect1> | |
67 | <title>Description</title> | |
68 | ||
69 | <para><function>sd_journal_stream_fd()</function> may be used to | |
70 | create a log stream file descriptor. Log messages written to this | |
71 | file descriptor as simple newline-separated text strings are | |
72 | written to the journal. This file descriptor can be used | |
73 | internally by applications or be made standard output or standard | |
74 | error of other processes executed.</para> | |
75 | ||
76 | <para><function>sd_journal_stream_fd()</function> takes a short | |
77 | program identifier string as first argument, which will be written | |
78 | to the journal as _SYSLOG_IDENTIFIER= field for each log entry | |
79 | (see | |
80 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
81 | for more information). The second argument shall be the default | |
82 | priority level for all messages. The priority level is one of | |
83 | <constant>LOG_EMERG</constant>, <constant>LOG_ALERT</constant>, | |
84 | <constant>LOG_CRIT</constant>, <constant>LOG_ERR</constant>, | |
85 | <constant>LOG_WARNING</constant>, <constant>LOG_NOTICE</constant>, | |
86 | <constant>LOG_INFO</constant>, <constant>LOG_DEBUG</constant>, as | |
87 | defined in <filename>syslog.h</filename>, see | |
88 | <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
89 | for details. The third argument is a boolean: if true kernel-style | |
90 | log level prefixes (such as <constant>SD_WARNING</constant>) are | |
91 | interpreted, see | |
92 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
93 | for more information.</para> | |
94 | ||
95 | <para>It is recommended that applications log UTF-8 messages only | |
96 | with this API, but this is not enforced.</para> | |
97 | </refsect1> | |
98 | ||
99 | <refsect1> | |
100 | <title>Return Value</title> | |
101 | ||
102 | <para>The call returns a valid write-only file descriptor on | |
103 | success or a negative errno-style error code.</para> | |
104 | </refsect1> | |
105 | ||
106 | <refsect1> | |
107 | <title>Notes</title> | |
108 | ||
b17649ee | 109 | <para>Function <function>sd_journal_stream_fd()</function> is thread-safe and may be called |
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110 | from multiple threads. All calls will return the same file descriptor, although temporarily |
111 | multiple file descriptors may be open.</para> | |
112 | ||
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113 | <para>The <function>sd_journal_stream_fd()</function> interface is |
114 | available as a shared library, which can be compiled and linked to | |
115 | with the | |
116 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
117 | file.</para> | |
118 | </refsect1> | |
119 | ||
120 | <refsect1> | |
121 | <title>Examples</title> | |
122 | ||
123 | <para>Creating a log stream suitable for | |
124 | <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>:</para> | |
125 | ||
126 | <programlisting>#include <syslog.h> | |
a81df0ad | 127 | #include <stdio.h> |
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128 | #include <string.h> |
129 | #include <unistd.h> | |
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130 | #include <systemd/sd-journal.h> |
131 | #include <systemd/sd-daemon.h> | |
132 | ||
133 | int main(int argc, char *argv[]) { | |
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134 | int fd; |
135 | FILE *log; | |
136 | fd = sd_journal_stream_fd("test", LOG_INFO, 1); | |
137 | if (fd < 0) { | |
138 | fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd)); | |
139 | return 1; | |
140 | } | |
141 | log = fdopen(fd, "w"); | |
142 | if (!log) { | |
143 | fprintf(stderr, "Failed to create file object: %m\n"); | |
144 | close(fd); | |
145 | return 1; | |
146 | } | |
147 | fprintf(log, "Hello World!\n"); | |
148 | fprintf(log, SD_WARNING "This is a warning!\n"); | |
149 | fclose(log); | |
150 | return 0; | |
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151 | }</programlisting> |
152 | ||
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153 | </refsect1> |
154 | ||
155 | <refsect1> | |
156 | <title>See Also</title> | |
157 | ||
158 | <para> | |
159 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
160 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
161 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
162 | <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
163 | <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
164 | <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
165 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
166 | </para> | |
167 | </refsect1> | |
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168 | |
169 | </refentry> |