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https://github.com/systemd/systemd
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138 lines
6.4 KiB
XML
138 lines
6.4 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/4.5/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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<refname>sd_journal_stream_fd_with_namespace</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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<funcprototype>
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<funcdef>int <function>sd_journal_stream_fd_with_namespace</function></funcdef>
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<paramdef>const char *<parameter>name_space</parameter></paramdef>
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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 create a log stream file descriptor.
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Log messages written to this file descriptor as simple newline-separated text strings are written
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to the journal. This file descriptor can be used internally by applications or be made standard output
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or standard error of other processes executed.</para>
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<para><function>sd_journal_stream_fd()</function> takes a short program identifier string as
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first argument, which will be written 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 priority level for all messages.
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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><function>sd_journal_stream_fd_with_namespace()</function> is similar to
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<function>sd_journal_stream_fd()</function>, but takes an additional <parameter>name_space</parameter> parameter
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that specifies which journal namespace to operate on. If specified as <constant>NULL</constant> the call
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is identical to <function>sd_journal_stream_fd()</function>. For details about journal namespaces, see
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<citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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<para>It is recommended that applications log UTF-8 messages only with this API, but this is not enforced.</para>
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<para>Each invocation of these functions 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
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is 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 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> and <function>sd_journal_stream_fd_with_namespace()</function>
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are "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>History</title>
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<para><function>sd_journal_stream_fd()</function> was added in version 187.</para>
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<para><function>sd_journal_stream_fd_with_namespace()</function> was added in version 256.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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