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11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
168 lines
6.1 KiB
XML
168 lines
6.1 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2012 Lennart Poettering
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-->
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<refentry id="sd_journal_stream_fd">
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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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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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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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<para>Function <function>sd_journal_stream_fd()</function> is thread-safe and may be called
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from multiple threads.</para>
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<para>The <function>sd_journal_stream_fd()</function> interface is
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available as a shared library, which can be compiled and linked to
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with the
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<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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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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