mirror of
https://github.com/systemd/systemd-stable.git
synced 2024-12-25 23:21:33 +03:00
246 lines
12 KiB
XML
246 lines
12 KiB
XML
<?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">
|
||
|
||
<!--
|
||
SPDX-License-Identifier: LGPL-2.1+
|
||
|
||
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 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 will 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 five 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-safety</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>, <function>sd_journal_sendv()</function> and
|
||
<function>sd_journal_perror()</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>
|