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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 | ||
5 | <!-- | |
6 | SPDX-License-Identifier: LGPL-2.1+ | |
7 | ||
8 | This file is part of systemd. | |
9 | ||
10 | Copyright 2012 Lennart Poettering | |
11 | --> | |
12 | ||
13 | <refentry id="sd_journal_stream_fd" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
14 | ||
15 | <refentryinfo> | |
16 | <title>sd_journal_stream_fd</title> | |
17 | <productname>systemd</productname> | |
18 | ||
19 | <authorgroup> | |
20 | <author> | |
21 | <contrib>Developer</contrib> | |
22 | <firstname>Lennart</firstname> | |
23 | <surname>Poettering</surname> | |
24 | <email>lennart@poettering.net</email> | |
25 | </author> | |
26 | </authorgroup> | |
27 | </refentryinfo> | |
28 | ||
29 | <refmeta> | |
30 | <refentrytitle>sd_journal_stream_fd</refentrytitle> | |
31 | <manvolnum>3</manvolnum> | |
32 | </refmeta> | |
33 | ||
34 | <refnamediv> | |
35 | <refname>sd_journal_stream_fd</refname> | |
36 | <refpurpose>Create log stream file descriptor to the journal</refpurpose> | |
37 | </refnamediv> | |
38 | ||
39 | <refsynopsisdiv> | |
40 | <funcsynopsis> | |
41 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
42 | ||
43 | <funcprototype> | |
44 | <funcdef>int <function>sd_journal_stream_fd</function></funcdef> | |
45 | <paramdef>const char *<parameter>identifier</parameter></paramdef> | |
46 | <paramdef>int <parameter>priority</parameter></paramdef> | |
47 | <paramdef>int <parameter>level_prefix</parameter></paramdef> | |
48 | </funcprototype> | |
49 | ||
50 | </funcsynopsis> | |
51 | </refsynopsisdiv> | |
52 | ||
53 | <refsect1> | |
54 | <title>Description</title> | |
55 | ||
56 | <para><function>sd_journal_stream_fd()</function> may be used to | |
57 | create a log stream file descriptor. Log messages written to this | |
58 | file descriptor as simple newline-separated text strings are | |
59 | written to the journal. This file descriptor can be used | |
60 | internally by applications or be made standard output or standard | |
61 | error of other processes executed.</para> | |
62 | ||
63 | <para><function>sd_journal_stream_fd()</function> takes a short | |
64 | program identifier string as first argument, which will be written | |
65 | to the journal as _SYSLOG_IDENTIFIER= field for each log entry | |
66 | (see | |
67 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
68 | for more information). The second argument shall be the default | |
69 | priority level for all messages. The priority level is one of | |
70 | <constant>LOG_EMERG</constant>, <constant>LOG_ALERT</constant>, | |
71 | <constant>LOG_CRIT</constant>, <constant>LOG_ERR</constant>, | |
72 | <constant>LOG_WARNING</constant>, <constant>LOG_NOTICE</constant>, | |
73 | <constant>LOG_INFO</constant>, <constant>LOG_DEBUG</constant>, as | |
74 | defined in <filename>syslog.h</filename>, see | |
75 | <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
76 | for details. The third argument is a boolean: if true kernel-style | |
77 | log level prefixes (such as <constant>SD_WARNING</constant>) are | |
78 | interpreted, see | |
79 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
80 | for more information.</para> | |
81 | ||
82 | <para>It is recommended that applications log UTF-8 messages only | |
83 | with this API, but this is not enforced.</para> | |
84 | ||
85 | <para>Each invocation of <function>sd_journal_stream_fd()</function> allocates a new log stream file descriptor, | |
86 | that is not shared with prior or later invocations. The file descriptor is write-only (its reading direction is | |
87 | shut down), and <constant>O_NONBLOCK</constant> is turned off initially.</para> | |
88 | </refsect1> | |
89 | ||
90 | <refsect1> | |
91 | <title>Return Value</title> | |
92 | ||
93 | <para>The call returns a valid write-only file descriptor on | |
94 | success or a negative errno-style error code.</para> | |
95 | </refsect1> | |
96 | ||
97 | <refsect1> | |
98 | <title>Signal safety</title> | |
99 | ||
100 | <para><function>sd_journal_stream_fd()</function> is "async signal safe" in the meaning of <citerefentry | |
101 | project='man-pages'><refentrytitle>signal-safety</refentrytitle><manvolnum>7</manvolnum></citerefentry>. | |
102 | </para> | |
103 | </refsect1> | |
104 | ||
105 | <refsect1> | |
106 | <title>Notes</title> | |
107 | ||
108 | <para>Function <function>sd_journal_stream_fd()</function> is thread-safe and may be called | |
109 | from multiple threads.</para> | |
110 | ||
111 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> | |
112 | </refsect1> | |
113 | ||
114 | <refsect1> | |
115 | <title>Examples</title> | |
116 | ||
117 | <para>Creating a log stream suitable for | |
118 | <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>:</para> | |
119 | ||
120 | <programlisting>#include <syslog.h> | |
121 | #include <stdio.h> | |
122 | #include <string.h> | |
123 | #include <unistd.h> | |
124 | #include <systemd/sd-journal.h> | |
125 | #include <systemd/sd-daemon.h> | |
126 | ||
127 | int main(int argc, char *argv[]) { | |
128 | int fd; | |
129 | FILE *log; | |
130 | fd = sd_journal_stream_fd("test", LOG_INFO, 1); | |
131 | if (fd < 0) { | |
132 | fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd)); | |
133 | return 1; | |
134 | } | |
135 | log = fdopen(fd, "w"); | |
136 | if (!log) { | |
137 | fprintf(stderr, "Failed to create file object: %m\n"); | |
138 | close(fd); | |
139 | return 1; | |
140 | } | |
141 | fprintf(log, "Hello World!\n"); | |
142 | fprintf(log, SD_WARNING "This is a warning!\n"); | |
143 | fclose(log); | |
144 | return 0; | |
145 | }</programlisting> | |
146 | ||
147 | </refsect1> | |
148 | ||
149 | <refsect1> | |
150 | <title>See Also</title> | |
151 | ||
152 | <para> | |
153 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
154 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
155 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
156 | <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
157 | <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
158 | <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
159 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
160 | </para> | |
161 | </refsect1> | |
162 | ||
163 | </refentry> |