]> git.ipfire.org Git - thirdparty/systemd.git/blob - man/sd_journal_stream_fd.xml
core: when looking for a UID to use for a dynamic UID start with the current owner...
[thirdparty/systemd.git] / man / sd_journal_stream_fd.xml
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 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_stream_fd">
25
26 <refentryinfo>
27 <title>sd_journal_stream_fd</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_stream_fd</refentrytitle>
42 <manvolnum>3</manvolnum>
43 </refmeta>
44
45 <refnamediv>
46 <refname>sd_journal_stream_fd</refname>
47 <refpurpose>Create log stream file descriptor to the journal</refpurpose>
48 </refnamediv>
49
50 <refsynopsisdiv>
51 <funcsynopsis>
52 <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
53
54 <funcprototype>
55 <funcdef>int <function>sd_journal_stream_fd</function></funcdef>
56 <paramdef>const char *<parameter>identifier</parameter></paramdef>
57 <paramdef>int <parameter>priority</parameter></paramdef>
58 <paramdef>int <parameter>level_prefix</parameter></paramdef>
59 </funcprototype>
60
61 </funcsynopsis>
62 </refsynopsisdiv>
63
64 <refsect1>
65 <title>Description</title>
66
67 <para><function>sd_journal_stream_fd()</function> may be used to
68 create a log stream file descriptor. Log messages written to this
69 file descriptor as simple newline-separated text strings are
70 written to the journal. This file descriptor can be used
71 internally by applications or be made standard output or standard
72 error of other processes executed.</para>
73
74 <para><function>sd_journal_stream_fd()</function> takes a short
75 program identifier string as first argument, which will be written
76 to the journal as _SYSLOG_IDENTIFIER= field for each log entry
77 (see
78 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
79 for more information). The second argument shall be the default
80 priority level for all messages. The priority level is one of
81 <constant>LOG_EMERG</constant>, <constant>LOG_ALERT</constant>,
82 <constant>LOG_CRIT</constant>, <constant>LOG_ERR</constant>,
83 <constant>LOG_WARNING</constant>, <constant>LOG_NOTICE</constant>,
84 <constant>LOG_INFO</constant>, <constant>LOG_DEBUG</constant>, as
85 defined in <filename>syslog.h</filename>, see
86 <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
87 for details. The third argument is a boolean: if true kernel-style
88 log level prefixes (such as <constant>SD_WARNING</constant>) are
89 interpreted, see
90 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
91 for more information.</para>
92
93 <para>It is recommended that applications log UTF-8 messages only
94 with this API, but this is not enforced.</para>
95 </refsect1>
96
97 <refsect1>
98 <title>Return Value</title>
99
100 <para>The call returns a valid write-only file descriptor on
101 success or a negative errno-style error code.</para>
102 </refsect1>
103
104 <refsect1>
105 <title>Notes</title>
106
107 <para>Function <function>sd_journal_stream_fd()</function> is thread-safe and may be called
108 from multiple threads. All calls will return the same file descriptor, although temporarily
109 multiple file descriptors may be open.</para>
110
111 <para>The <function>sd_journal_stream_fd()</function> interface is
112 available as a shared library, which can be compiled and linked to
113 with the
114 <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
115 file.</para>
116 </refsect1>
117
118 <refsect1>
119 <title>Examples</title>
120
121 <para>Creating a log stream suitable for
122 <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>:</para>
123
124 <programlisting>#include &lt;syslog.h&gt;
125 #include &lt;stdio.h&gt;
126 #include &lt;string.h&gt;
127 #include &lt;unistd.h&gt;
128 #include &lt;systemd/sd-journal.h&gt;
129 #include &lt;systemd/sd-daemon.h&gt;
130
131 int main(int argc, char *argv[]) {
132 int fd;
133 FILE *log;
134 fd = sd_journal_stream_fd("test", LOG_INFO, 1);
135 if (fd &lt; 0) {
136 fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd));
137 return 1;
138 }
139 log = fdopen(fd, "w");
140 if (!log) {
141 fprintf(stderr, "Failed to create file object: %m\n");
142 close(fd);
143 return 1;
144 }
145 fprintf(log, "Hello World!\n");
146 fprintf(log, SD_WARNING "This is a warning!\n");
147 fclose(log);
148 return 0;
149 }</programlisting>
150
151 </refsect1>
152
153 <refsect1>
154 <title>See Also</title>
155
156 <para>
157 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
158 <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
159 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
160 <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
161 <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
162 <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
163 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
164 </para>
165 </refsect1>
166
167 </refentry>