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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 <systemd/sd-journal.h></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 standard output or standard
error 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 <constant>LOG_EMERG</constant>,
<constant>LOG_ALERT</constant>,
<constant>LOG_CRIT</constant>,
<constant>LOG_ERR</constant>,
<constant>LOG_WARNING</constant>,
<constant>LOG_NOTICE</constant>,
<constant>LOG_INFO</constant>,
<constant>LOG_DEBUG</constant>, 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
<constant>SD_WARNING</constant>) 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
messages 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 a shared library, which can
be compiled and linked to with the
<constant>libsystemd</constant> <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 <syslog.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <systemd/sd-journal.h>
#include <systemd/sd-daemon.h>
int main(int argc, char *argv[]) {
int fd;
FILE *log;
fd = sd_journal_stream_fd("test", LOG_INFO, 1);
if (fd < 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);
return 0;
}</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>
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