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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 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
7d6b2723 | 9 | <refentry id="sd_journal_stream_fd" xmlns:xi="http://www.w3.org/2001/XInclude"> |
a81df0ad | 10 | |
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11 | <refentryinfo> |
12 | <title>sd_journal_stream_fd</title> | |
13 | <productname>systemd</productname> | |
14 | ||
15 | <authorgroup> | |
16 | <author> | |
17 | <contrib>Developer</contrib> | |
18 | <firstname>Lennart</firstname> | |
19 | <surname>Poettering</surname> | |
20 | <email>lennart@poettering.net</email> | |
21 | </author> | |
22 | </authorgroup> | |
23 | </refentryinfo> | |
24 | ||
25 | <refmeta> | |
26 | <refentrytitle>sd_journal_stream_fd</refentrytitle> | |
27 | <manvolnum>3</manvolnum> | |
28 | </refmeta> | |
29 | ||
30 | <refnamediv> | |
31 | <refname>sd_journal_stream_fd</refname> | |
32 | <refpurpose>Create log stream file descriptor to the journal</refpurpose> | |
33 | </refnamediv> | |
34 | ||
35 | <refsynopsisdiv> | |
36 | <funcsynopsis> | |
37 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
38 | ||
39 | <funcprototype> | |
40 | <funcdef>int <function>sd_journal_stream_fd</function></funcdef> | |
41 | <paramdef>const char *<parameter>identifier</parameter></paramdef> | |
42 | <paramdef>int <parameter>priority</parameter></paramdef> | |
43 | <paramdef>int <parameter>level_prefix</parameter></paramdef> | |
44 | </funcprototype> | |
45 | ||
46 | </funcsynopsis> | |
47 | </refsynopsisdiv> | |
48 | ||
49 | <refsect1> | |
50 | <title>Description</title> | |
51 | ||
52 | <para><function>sd_journal_stream_fd()</function> may be used to | |
53 | create a log stream file descriptor. Log messages written to this | |
54 | file descriptor as simple newline-separated text strings are | |
55 | written to the journal. This file descriptor can be used | |
56 | internally by applications or be made standard output or standard | |
57 | error of other processes executed.</para> | |
58 | ||
59 | <para><function>sd_journal_stream_fd()</function> takes a short | |
60 | program identifier string as first argument, which will be written | |
61 | to the journal as _SYSLOG_IDENTIFIER= field for each log entry | |
62 | (see | |
63 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
64 | for more information). The second argument shall be the default | |
65 | priority level for all messages. The priority level is one of | |
66 | <constant>LOG_EMERG</constant>, <constant>LOG_ALERT</constant>, | |
67 | <constant>LOG_CRIT</constant>, <constant>LOG_ERR</constant>, | |
68 | <constant>LOG_WARNING</constant>, <constant>LOG_NOTICE</constant>, | |
69 | <constant>LOG_INFO</constant>, <constant>LOG_DEBUG</constant>, as | |
70 | defined in <filename>syslog.h</filename>, see | |
71 | <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
72 | for details. The third argument is a boolean: if true kernel-style | |
73 | log level prefixes (such as <constant>SD_WARNING</constant>) are | |
74 | interpreted, see | |
75 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
76 | for more information.</para> | |
77 | ||
78 | <para>It is recommended that applications log UTF-8 messages only | |
79 | with this API, but this is not enforced.</para> | |
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80 | |
81 | <para>Each invocation of <function>sd_journal_stream_fd()</function> allocates a new log stream file descriptor, | |
82 | that is not shared with prior or later invocations. The file descriptor is write-only (its reading direction is | |
83 | shut down), and <constant>O_NONBLOCK</constant> is turned off initially.</para> | |
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84 | </refsect1> |
85 | ||
86 | <refsect1> | |
87 | <title>Return Value</title> | |
88 | ||
89 | <para>The call returns a valid write-only file descriptor on | |
90 | success or a negative errno-style error code.</para> | |
91 | </refsect1> | |
92 | ||
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93 | <refsect1> |
94 | <title>Signal safety</title> | |
95 | ||
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96 | <para><function>sd_journal_stream_fd()</function> is "async signal safe" in the meaning of <citerefentry |
97 | project='man-pages'><refentrytitle>signal-safety</refentrytitle><manvolnum>7</manvolnum></citerefentry>. | |
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98 | </para> |
99 | </refsect1> | |
100 | ||
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101 | <refsect1> |
102 | <title>Notes</title> | |
103 | ||
b17649ee | 104 | <para>Function <function>sd_journal_stream_fd()</function> is thread-safe and may be called |
bf105e38 | 105 | from multiple threads.</para> |
a8d46a16 | 106 | |
7d6b2723 | 107 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> |
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108 | </refsect1> |
109 | ||
110 | <refsect1> | |
111 | <title>Examples</title> | |
112 | ||
113 | <para>Creating a log stream suitable for | |
114 | <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>:</para> | |
115 | ||
116 | <programlisting>#include <syslog.h> | |
a81df0ad | 117 | #include <stdio.h> |
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118 | #include <string.h> |
119 | #include <unistd.h> | |
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120 | #include <systemd/sd-journal.h> |
121 | #include <systemd/sd-daemon.h> | |
122 | ||
123 | int main(int argc, char *argv[]) { | |
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124 | int fd; |
125 | FILE *log; | |
126 | fd = sd_journal_stream_fd("test", LOG_INFO, 1); | |
127 | if (fd < 0) { | |
128 | fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd)); | |
129 | return 1; | |
130 | } | |
131 | log = fdopen(fd, "w"); | |
132 | if (!log) { | |
133 | fprintf(stderr, "Failed to create file object: %m\n"); | |
134 | close(fd); | |
135 | return 1; | |
136 | } | |
137 | fprintf(log, "Hello World!\n"); | |
138 | fprintf(log, SD_WARNING "This is a warning!\n"); | |
139 | fclose(log); | |
140 | return 0; | |
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141 | }</programlisting> |
142 | ||
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143 | </refsect1> |
144 | ||
145 | <refsect1> | |
146 | <title>See Also</title> | |
147 | ||
148 | <para> | |
149 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
150 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
151 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
152 | <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
153 | <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
154 | <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
155 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
156 | </para> | |
157 | </refsect1> | |
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158 | |
159 | </refentry> |