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https://github.com/systemd/systemd
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![Zbigniew Jędrzejewski-Szmek](/assets/img/avatar_default.png)
The "include" files had type "book" for some raeason. I don't think this is meaningful. Let's just use the same everywhere. $ perl -i -0pe 's^..DOCTYPE (book|refentry) PUBLIC "-//OASIS//DTD DocBook XML V4.[25]//EN"\s+"http^<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"\n "http^gms' man/*.xml
147 lines
5.5 KiB
XML
147 lines
5.5 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+ -->
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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>#include <syslog.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <systemd/sd-journal.h>
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#include <systemd/sd-daemon.h>
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int main(int argc, char *argv[]) {
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int fd;
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FILE *log;
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fd = sd_journal_stream_fd("test", LOG_INFO, 1);
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if (fd < 0) {
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fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd));
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return 1;
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}
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log = fdopen(fd, "w");
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if (!log) {
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fprintf(stderr, "Failed to create file object: %m\n");
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close(fd);
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return 1;
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}
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fprintf(log, "Hello World!\n");
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fprintf(log, SD_WARNING "This is a warning!\n");
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fclose(log);
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return 0;
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}</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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