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92fba83e3a
Sometimes an entry is not successfully written, and we end up with data items which are "unlinked", not connected to, and not used by any entry. This will usually happen when we write to write a core dump, and the initial small data fields are written successfully, but the huge COREDUMP= field is not written. This situation is hard to avoid, but the results are mostly harmless. Thus only warn about unused data items. Also, be more verbose about why journal files failed verification. This should help diagnose journal failure modes without resorting to a hexadecimal editor. https://bugs.freedesktop.org/show_bug.cgi?id=65235 (esp. see system.journal attached to the bug report).
252 lines
13 KiB
XML
252 lines
13 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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This file is part of systemd.
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Copyright 2012 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_journal_print">
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<refentryinfo>
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<title>sd_journal_print</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_print</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_print</refname>
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<refname>sd_journal_printv</refname>
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<refname>sd_journal_send</refname>
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<refname>sd_journal_sendv</refname>
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<refname>sd_journal_perror</refname>
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<refname>SD_JOURNAL_SUPPRESS_LOCATION</refname>
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<refpurpose>Submit log entries 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_print</function></funcdef>
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<paramdef>int <parameter>priority</parameter></paramdef>
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<paramdef>const char* <parameter>format</parameter></paramdef>
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<paramdef>...</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_printv</function></funcdef>
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<paramdef>int <parameter>priority</parameter></paramdef>
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<paramdef>const char* <parameter>format</parameter></paramdef>
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<paramdef>va_list <parameter>ap</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_send</function></funcdef>
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<paramdef>const char* <parameter>format</parameter></paramdef>
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<paramdef>...</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_sendv</function></funcdef>
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<paramdef>const struct iovec *<parameter>iov</parameter></paramdef>
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<paramdef>int <parameter>n</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_perror</function></funcdef>
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<paramdef>const char* <parameter>message</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_print()</function> may be
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used to submit simple, plain text log entries to the
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system journal. The first argument is a priority
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value. This is followed by a format string and its
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parameters, similar to
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<citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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or
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<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
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priority value is one of
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<literal>LOG_EMERG</literal>,
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<literal>LOG_ALERT</literal>,
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<literal>LOG_CRIT</literal>,
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<literal>LOG_ERR</literal>,
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<literal>LOG_WARNING</literal>,
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<literal>LOG_NOTICE</literal>,
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<literal>LOG_INFO</literal>,
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<literal>LOG_DEBUG</literal>, as defined in
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<filename>syslog.h</filename>, see
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<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for details. It is recommended to use this call to
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submit log messages in the application locale or system
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locale and in UTF-8 format, but no such restrictions
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are enforced.</para>
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<para><function>sd_journal_printv()</function> is
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similar to <function>sd_journal_print()</function> but
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takes a variable argument list encapsulated in an
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object of type <literal>va_list</literal> (see
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<citerefentry><refentrytitle>stdarg</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for more information) instead of the format string. It
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is otherwise equivalent in behavior.</para>
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<para><function>sd_journal_send()</function> may be
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used to submit structured log entries to the system
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journal. It takes a series of format strings, each
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immediately followed by their associated parameters,
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terminated by NULL. The strings passed should be of
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the format <literal>VARIABLE=value</literal>. The
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variable name must be in uppercase and consist only of
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characters, numbers and underscores, and may not begin
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with an underscore. (All assignments that do not
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follow this syntax will be ignored.) The value can be
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of any size and format. It is highly recommended to
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submit text strings formatted in the UTF-8 character
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encoding only, and submit binary fields only when
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formatting in UTF-8 strings is not sensible. A number
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of well known fields are defined, see
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for details, but additional application defined fields
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may be used. A variable may be assigned more than one
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value per entry.</para>
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<para><function>sd_journal_sendv()</function> is
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similar to <function>sd_journal_send()</function> but
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takes an array of <literal>struct iovec</literal> (as
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defined in <filename>uio.h</filename>, see
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<citerefentry><refentrytitle>readv</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for details) instead of the format string. Each
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structure should reference one field of the entry to
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submit. The second argument specifies the number of
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structures in the
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array. <function>sd_journal_sendv()</function> is
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particularly useful to submit binary objects to the
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journal where that is necessary.</para>
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<para><function>sd_journal_perror()</function> is a
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similar to
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<citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and writes a message to the journal that consists of
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the passed string, suffixed with ": " and a human
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readable representation of the current error code
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stored in
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<citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
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the message string is passed as NULL or empty string
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only the error string representation will be written,
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prefixed with nothing. An additional journal field
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ERRNO= is included in the entry containing the numeric
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error code formatted as decimal string. The log
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priority used is <literal>LOG_ERR</literal> (3).</para>
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<para>Note that <function>sd_journal_send()</function>
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is a wrapper around
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<function>sd_journal_sendv()</function> to make it
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easier to use when only text strings shall be
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submitted. Also, the following two calls are
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mostly equivalent:</para>
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<programlisting>sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid());
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sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(),
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"PRIORITY=%i", LOG_INFO,
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NULL);</programlisting>
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<para>Note that these calls implicitly add fields for
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the source file, function name and code line where
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invoked. This is implemented with macros. If this is
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not desired it can be turned off by defining
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SD_JOURNAL_SUPPRESS_LOCATION before including
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<filename>sd-journal.h</filename>.</para>
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<para><citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and <function>sd_journal_print()</function> may
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largely be used interchangeably
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functionality-wise. However, note that log messages
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logged via the former take a different path to the
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journal server than the later, and hence global
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chronological ordering between the two streams cannot
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be guaranteed. Using
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<function>sd_journal_print()</function> has the
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benefit of logging source code line, file names, and
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functions as meta data along all entries, and
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guaranteeing chronological ordering with structured
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log entries that are generated via
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<function>sd_journal_send()</function>. Using
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<function>syslog()</function> has the benefit of being
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more portable.</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 four calls return 0 on success or a negative
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errno-style error code. The
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<citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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variable itself is not altered.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>The <function>sd_journal_print()</function>,
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<function>sd_journal_printv()</function>,
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<function>sd_journal_send()</function> and
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<function>sd_journal_sendv()</function> interfaces
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are available as shared library, which can be compiled
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and linked to with the
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<literal>libsystemd-journal</literal>
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<citerefentry><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>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_journal_stream_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>errno</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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