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This way it's much easier to test that the code compiles without issues. It's also easier to edit the code. Indentation in one of the examples is reduced to two spaces. This is what we use in man pages to make them fit on screen better.
121 lines
5 KiB
XML
121 lines
5 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_journal_stream_fd" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_journal_stream_fd</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_journal_stream_fd</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_journal_stream_fd</refname>
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<refpurpose>Create log stream file descriptor to the journal</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_journal_stream_fd</function></funcdef>
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<paramdef>const char *<parameter>identifier</parameter></paramdef>
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<paramdef>int <parameter>priority</parameter></paramdef>
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<paramdef>int <parameter>level_prefix</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_journal_stream_fd()</function> may be used to
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create a log stream file descriptor. Log messages written to this
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file descriptor as simple newline-separated text strings are
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written to the journal. This file descriptor can be used
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internally by applications or be made standard output or standard
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error of other processes executed.</para>
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<para><function>sd_journal_stream_fd()</function> takes a short
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program identifier string as first argument, which will be written
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to the journal as SYSLOG_IDENTIFIER= field for each log entry
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(see
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for more information). The second argument shall be the default
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priority level for all messages. The priority level is one of
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<constant>LOG_EMERG</constant>, <constant>LOG_ALERT</constant>,
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<constant>LOG_CRIT</constant>, <constant>LOG_ERR</constant>,
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<constant>LOG_WARNING</constant>, <constant>LOG_NOTICE</constant>,
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<constant>LOG_INFO</constant>, <constant>LOG_DEBUG</constant>, as
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defined in <filename>syslog.h</filename>, see
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<citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for details. The third argument is a boolean: if true kernel-style
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log level prefixes (such as <constant>SD_WARNING</constant>) are
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interpreted, see
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<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for more information.</para>
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<para>It is recommended that applications log UTF-8 messages only
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with this API, but this is not enforced.</para>
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<para>Each invocation of <function>sd_journal_stream_fd()</function> allocates a new log stream file descriptor,
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that is not shared with prior or later invocations. The file descriptor is write-only (its reading direction is
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shut down), and <constant>O_NONBLOCK</constant> is turned off initially.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>The call returns a valid write-only file descriptor on
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success or a negative errno-style error code.</para>
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</refsect1>
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<refsect1>
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<title>Signal safety</title>
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<para><function>sd_journal_stream_fd()</function> is "async signal safe" in the meaning of <citerefentry
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project='man-pages'><refentrytitle>signal-safety</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
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</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<xi:include href="threads-aware.xml" xpointer="safe"/>
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<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>Creating a log stream suitable for
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<citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>:</para>
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<programlisting><xi:include href="journal-stream-fd.c" parse="text" /></programlisting>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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