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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 &lt;systemd/sd-journal.h&gt;</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 project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
+ <citerefentry project='man-pages'><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
+ project='man-pages'><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. Note that log messages written using this function are generally not
+ expected to end in a new-line character. However, as all trailing whitespace (including spaces, new-lines,
+ tabulators and carriage returns) are automatically stripped from the logged string, it is acceptable to specify one
+ (or more). Empty lines (after trailing whitespace removal) are suppressed. On non-empty lines, leading whitespace
+ (as well as inner whitespace) is left unmodified. </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 project='man-pages'><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. If this function is used, trailing whitespace is automatically removed from each formatted field.</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
+ project='man-pages'><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. Note that this function wil not strip trailing
+ whitespace of the passed fields, but passes the specified data along unmodified. This is different from both
+ <function>sd_journal_print()</function> and <function>sd_journal_send()</function> described above, which are based
+ on format strings, and do strip trailing whitespace.</para>
+
+ <para><function>sd_journal_perror()</function> is a similar to
+ <citerefentry project='die-net'><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 project='man-pages'><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 project='man-pages'><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 metadata 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 project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ variable itself is not altered.</para>
+
+ <para>If
+ <citerefentry><refentrytitle>systemd-journald</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ is not running (the socket is not present), those functions do
+ nothing, and also return 0.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Thread safety</title>
+ <para>All functions listed here are thread-safe and may be called in parallel from multiple threads.</para>
+
+ <para><function>sd_journal_sendv()</function> is "async signal safe" in the meaning of
+ <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ </para>
+
+ <para><function>sd_journal_print</function>,
+ <function>sd_journal_printv</function>,
+ <function>sd_journal_send</function>, and
+ <function>sd_journal_perror</function> are
+ not async signal safe.</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 a shared library, which can be compiled and linked to with the
+ <constant>libsystemd</constant> <citerefentry project='die-net'><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 project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='die-net'><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>