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">
6 This file is part of systemd.
8 Copyright 2012 Lennart Poettering
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.
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.
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/>.
24 <refentry id="sd_journal_stream_fd">
27 <title>sd_journal_stream_fd</title>
28 <productname>systemd</productname>
32 <contrib>Developer</contrib>
33 <firstname>Lennart</firstname>
34 <surname>Poettering</surname>
35 <email>lennart@poettering.net</email>
41 <refentrytitle>sd_journal_stream_fd</refentrytitle>
42 <manvolnum>3</manvolnum>
46 <refname>sd_journal_stream_fd</refname>
47 <refpurpose>Create log stream file descriptor to the journal</refpurpose>
52 <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
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>
65 <title>Description</title>
67 <para><function>sd_journal_stream_fd()</function> may
68 be used to create a log stream file descriptor. Log
69 messages written to this file descriptor as simple
70 newline-separated text strings are written to the
71 journal. This file descriptor can be used internally
72 by applications or be made STDOUT/STDERR of other
73 processes executed.</para>
75 <para><function>sd_journal_stream_fd()</function>
76 takes a short program identifier string as first
77 argument, which will be written to the journal as
78 _SYSLOG_IDENTIFIER= field for each log entry (see
79 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
80 for more information). The second argument shall be
81 the default priority level for all messages. The
82 priority level is one of <constant>LOG_EMERG</constant>,
83 <constant>LOG_ALERT</constant>,
84 <constant>LOG_CRIT</constant>,
85 <constant>LOG_ERR</constant>,
86 <constant>LOG_WARNING</constant>,
87 <constant>LOG_NOTICE</constant>,
88 <constant>LOG_INFO</constant>,
89 <constant>LOG_DEBUG</constant>, as defined in
90 <filename>syslog.h</filename>, see
91 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
92 for details. The third argument is a boolean: if true
93 kernel-style log priority level prefixes (such as
94 <constant>SD_WARNING</constant>) are interpreted, see
95 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
96 for more information.</para>
98 <para>It is recommended that applications log UTF-8
99 messages only with this API, but this is not
105 <title>Return Value</title>
107 <para>The call returns a valid write-only file descriptor on success or a
108 negative errno-style error code.</para>
114 <para>The <function>sd_journal_stream_fd()</function>
115 interface is available as shared library, which can
116 be compiled and linked to with the
117 <constant>libsystemd-journal</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
122 <title>Examples</title>
124 <para>Creating a log stream suitable for
125 <citerefentry><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>:</para>
127 <programlisting>#include <syslog.h>
128 #include <stdio.h>
129 #include <string.h>
130 #include <unistd.h>
131 #include <systemd/sd-journal.h>
132 #include <systemd/sd-daemon.h>
134 int main(int argc, char *argv[]) {
137 fd = sd_journal_stream_fd("test", LOG_INFO, 1);
139 fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd));
142 log = fdopen(fd, "w");
144 fprintf(stderr, "Failed to create file object: %m\n");
148 fprintf(log, "Hello World!\n");
149 fprintf(log, SD_WARNING "This is a warning!\n");
157 <title>See Also</title>
160 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
161 <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
162 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
163 <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
164 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
165 <citerefentry><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
166 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>