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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2012 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_journal_print">
<refentryinfo>
<title>sd_journal_print</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_journal_print</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_journal_print</refname>
<refname>sd_journal_printv</refname>
<refname>sd_journal_send</refname>
<refname>sd_journal_sendv</refname>
<refname>sd_journal_perror</refname>
<refname>SD_JOURNAL_SUPPRESS_LOCATION</refname>
<refpurpose>Submit log entries to the journal</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_journal_print</function></funcdef>
<paramdef>int <parameter>priority</parameter></paramdef>
<paramdef>const char* <parameter>format</parameter></paramdef>
<paramdef>...</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_printv</function></funcdef>
<paramdef>int <parameter>priority</parameter></paramdef>
<paramdef>const char* <parameter>format</parameter></paramdef>
<paramdef>va_list <parameter>ap</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_send</function></funcdef>
<paramdef>const char* <parameter>format</parameter></paramdef>
<paramdef>...</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_sendv</function></funcdef>
<paramdef>const struct iovec *<parameter>iov</parameter></paramdef>
<paramdef>int <parameter>n</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_perror</function></funcdef>
<paramdef>const char* <parameter>message</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_journal_print()</function> may be
used to submit simple, plain text log entries to the
system journal. The first argument is a priority
value. This is followed by a format string and its
parameters, similar to
<citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
or
<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
priority value is one of
<constant>LOG_EMERG</constant>,
<constant>LOG_ALERT</constant>,
<constant>LOG_CRIT</constant>,
<constant>LOG_ERR</constant>,
<constant>LOG_WARNING</constant>,
<constant>LOG_NOTICE</constant>,
<constant>LOG_INFO</constant>,
<constant>LOG_DEBUG</constant>, as defined in
<filename>syslog.h</filename>, see
<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for details. It is recommended to use this call to
submit log messages in the application locale or system
locale and in UTF-8 format, but no such restrictions
are enforced.</para>
<para><function>sd_journal_printv()</function> is
similar to <function>sd_journal_print()</function> but
takes a variable argument list encapsulated in an
object of type <varname>va_list</varname> (see
<citerefentry><refentrytitle>stdarg</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for more information) instead of the format string. It
is otherwise equivalent in behavior.</para>
<para><function>sd_journal_send()</function> may be
used to submit structured log entries to the system
journal. It takes a series of format strings, each
immediately followed by their associated parameters,
terminated by <constant>NULL</constant>. The strings passed should be of
the format <literal>VARIABLE=value</literal>. The
variable name must be in uppercase and consist only of
characters, numbers and underscores, and may not begin
with an underscore. (All assignments that do not
follow this syntax will be ignored.) The value can be
of any size and format. It is highly recommended to
submit text strings formatted in the UTF-8 character
encoding only, and submit binary fields only when
formatting in UTF-8 strings is not sensible. A number
of well known fields are defined, see
<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for details, but additional application defined fields
may be used. A variable may be assigned more than one
value per entry.</para>
<para><function>sd_journal_sendv()</function> is
similar to <function>sd_journal_send()</function> but
takes an array of <varname>struct iovec</varname> (as
defined in <filename>uio.h</filename>, see
<citerefentry><refentrytitle>readv</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for details) instead of the format string. Each
structure should reference one field of the entry to
submit. The second argument specifies the number of
structures in the
array. <function>sd_journal_sendv()</function> is
particularly useful to submit binary objects to the
journal where that is necessary.</para>
<para><function>sd_journal_perror()</function> is a
similar to
<citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>
and writes a message to the journal that consists of
the passed string, suffixed with ": " and a human
readable representation of the current error code
stored in
<citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
the message string is passed as <constant>NULL</constant> or empty string
only the error string representation will be written,
prefixed with nothing. An additional journal field
ERRNO= is included in the entry containing the numeric
error code formatted as decimal string. The log
priority used is <constant>LOG_ERR</constant> (3).</para>
<para>Note that <function>sd_journal_send()</function>
is a wrapper around
<function>sd_journal_sendv()</function> to make it
easier to use when only text strings shall be
submitted. Also, the following two calls are
mostly equivalent:</para>
<programlisting>sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid());
sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(),
"PRIORITY=%i", LOG_INFO,
NULL);</programlisting>
<para>Note that these calls implicitly add fields for
the source file, function name and code line where
invoked. This is implemented with macros. If this is
not desired it can be turned off by defining
SD_JOURNAL_SUPPRESS_LOCATION before including
<filename>sd-journal.h</filename>.</para>
<para><citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
and <function>sd_journal_print()</function> may
largely be used interchangeably
functionality-wise. However, note that log messages
logged via the former take a different path to the
journal server than the later, and hence global
chronological ordering between the two streams cannot
be guaranteed. Using
<function>sd_journal_print()</function> has the
benefit of logging source code line, filenames, and
functions as meta data along all entries, and
guaranteeing chronological ordering with structured
log entries that are generated via
<function>sd_journal_send()</function>. Using
<function>syslog()</function> has the benefit of being
more portable.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>The four calls return 0 on success or a negative
errno-style error code. The
<citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
variable itself is not altered.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_journal_print()</function>,
<function>sd_journal_printv()</function>,
<function>sd_journal_send()</function> and
<function>sd_journal_sendv()</function> interfaces
are available as shared library, which can be compiled
and linked to with the
<constant>libsystemd-journal</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_stream_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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