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5aded36978
It is annoying when we have dead links on fd.o. Add project='man-pages|die-net|archlinux' to <citerefentry>-ies. In generated html, add external links to http://man7.org/linux/man-pages/man, http://linux.die.net/man/, https://www.archlinux.org/. By default, pages in sections 2 and 4 go to man7, since Michael Kerrisk is the autorative source on kernel related stuff. The rest of links goes to linux.die.net, because they have the manpages. Except for the pacman stuff, since it seems to be only available from archlinux.org. Poor gummiboot gets no link, because gummitboot(8) ain't to be found on the net. According to common wisdom, that would mean that it does not exist. But I have seen Kay using it, so I know it does, and deserves to be found. Can somebody be nice and put it up somewhere?
271 lines
14 KiB
XML
271 lines
14 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 project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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or
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<citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
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priority value is one of
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<constant>LOG_EMERG</constant>,
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<constant>LOG_ALERT</constant>,
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<constant>LOG_CRIT</constant>,
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<constant>LOG_ERR</constant>,
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<constant>LOG_WARNING</constant>,
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<constant>LOG_NOTICE</constant>,
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<constant>LOG_INFO</constant>,
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<constant>LOG_DEBUG</constant>, as defined in
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<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. 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 <varname>va_list</varname> (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 <constant>NULL</constant>. 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 <varname>struct iovec</varname> (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 array.
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<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 project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
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the message string is passed as <constant>NULL</constant> 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 <constant>LOG_ERR</constant> (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 project='man-pages'><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, filenames, and
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functions as metadata 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 project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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variable itself is not altered.</para>
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<para>If
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<citerefentry><refentrytitle>systemd-journald</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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is not running (the socket is not present), those
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functions do nothing, and also return 0.</para>
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</refsect1>
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<refsect1>
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<title>Async signal safety</title>
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<para><function>sd_journal_sendv()</function> is "async signal
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safe" in the meaning of <citerefentry><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
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</para>
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<para><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_perror</function> are
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not async signal safe.</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 a shared library, which can be compiled
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and linked to 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>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 project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><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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<citerefentry><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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