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authorLennart Poettering <lennart@poettering.net>2012-07-13 02:18:45 +0200
committerLennart Poettering <lennart@poettering.net>2012-07-13 02:18:45 +0200
commita81df0ad90f0dea0eb272c02efe18934fa66fdf2 (patch)
tree8374fc80f595dcc008cda5ad56d647e9ef023b19 /man
parentcb07866b1b7c11e687a322d70dd9f9d73bbbe488 (diff)
man: document sd_journal_stream_fd()
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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+ This file is part of systemd.
+
+ Copyright 2012 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_journal_stream_fd">
+
+ <refentryinfo>
+ <title>sd_journal_stream_fd</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_journal_stream_fd</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_journal_stream_fd</refname>
+ <refpurpose>Create log stream file descriptor to the journal</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_stream_fd</function></funcdef>
+ <paramdef>const char* <parameter>identifier</parameter></paramdef>
+ <paramdef>int <parameter>priority</parameter></paramdef>
+ <paramdef>int <parameter>level_prefix</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_journal_stream_fd()</function> may
+ be used to create a log stream file descriptor. Log
+ messages written to this file descriptor as simple
+ newline separated text strings are written to the
+ journal. This file descriptor can be used internally
+ by applications or be made STDOUT/STDERR of other
+ processes executed.</para>
+
+ <para><function>sd_journal_stream_fd()</function>
+ takes a short program identifier string as first
+ argument, which will be written to the journal as
+ _SYSLOG_IDENTIFIER= field for each log entry (see
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ for more information). The second argument shall be
+ the default priority level for all messages. The
+ priority level is one of <literal>LOG_EMERG</literal>,
+ <literal>LOG_ALERT</literal>,
+ <literal>LOG_CRIT</literal>,
+ <literal>LOG_ERR</literal>,
+ <literal>LOG_WARNING</literal>,
+ <literal>LOG_NOTICE</literal>,
+ <literal>LOG_INFO</literal>,
+ <literal>LOG_DEBUG</literal>, as defined in
+ <filename>syslog.h</filename>, see
+ <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for details. The third argument is a boolean: if true
+ kernel-style log priority level prefixes (such as
+ <literal>SD_WARNING</literal>) are interpreted, see
+ <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for more information.</para>
+
+ <para>It is recommended that applications log UTF-8
+ mesages only with this API, but this is not
+ enforced.</para>
+
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>The call returns a valid write-only file descriptor on success or a
+ negative errno-style error code.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>The <function>sd_journal_stream_fd()</function>
+ interface is available as shared library, which can
+ be compiled and linked to with the
+ <literal>libsystemd-journal</literal>
+ <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ file.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <para>Creating a log stream suitable for
+ <citerefentry><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>:</para>
+
+ <programlisting>#include &lt;syslog.h&gt;
+#include &lt;stdio.h&gt;
+#include &lt;systemd/sd-journal.h&gt;
+#include &lt;systemd/sd-daemon.h&gt;
+
+int main(int argc, char *argv[]) {
+ int fd;
+ FILE *log;
+ fd = sd_journal_stream_fd("test", LOG_INFO, 1);
+ if (fd &lt; 0) {
+ fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd));
+ return 1;
+ }
+ log = fdopen(fd, "w");
+ if (!log) {
+ fprintf(stderr, "Failed to create file object: %m\n");
+ close(fd);
+ return 1;
+ }
+ fprintf(log, "Hello World!\n");
+ fprintf(log, SD_WARNING "This is a warning!\n");
+ fclose(log);
+}</programlisting>
+
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>