[thirdparty/systemd.git] / man / sd_journal_print.xml

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        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

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  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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  You should have received a copy of the GNU Lesser General Public License
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<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><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 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><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                variable itself is not altered.</para>
        </refsect1>

        <refsect1>
                <title>Async signal safety</title>
                <para><function>sd_journal_sendv()</function> is "async signal
                safe" in the meaning of <citerefentry><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><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>,
                        <citerefentry><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>
Commit	Line	Data
a8eedf49 LP	1	<?xml version='1.0'?> <!---nxml--->
	2	<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
	3	"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
	4
	5	<!--
	6	This file is part of systemd.
	7
	8	Copyright 2012 Lennart Poettering
	9
	10	systemd is free software; you can redistribute it and/or modify it
	11	under the terms of the GNU Lesser General Public License as published by
	12	the Free Software Foundation; either version 2.1 of the License, or
	13	(at your option) any later version.
	14
	15	systemd is distributed in the hope that it will be useful, but
	16	WITHOUT ANY WARRANTY; without even the implied warranty of
	17	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	18	Lesser General Public License for more details.
	19
	20	You should have received a copy of the GNU Lesser General Public License
	21	along with systemd; If not, see <http://www.gnu.org/licenses/>.
	22	-->
	23
	24	<refentry id="sd_journal_print">
	25
	26	<refentryinfo>
	27	<title>sd_journal_print</title>
	28	<productname>systemd</productname>
	29
	30	<authorgroup>
	31	<author>
	32	<contrib>Developer</contrib>
	33	<firstname>Lennart</firstname>
	34	<surname>Poettering</surname>
	35	<email>lennart@poettering.net</email>
	36	</author>
	37	</authorgroup>
	38	</refentryinfo>
	39
	40	<refmeta>
	41	<refentrytitle>sd_journal_print</refentrytitle>
	42	<manvolnum>3</manvolnum>
	43	</refmeta>
	44
	45	<refnamediv>
	46	<refname>sd_journal_print</refname>
	47	<refname>sd_journal_printv</refname>
	48	<refname>sd_journal_send</refname>
	49	<refname>sd_journal_sendv</refname>
18c7ed18	50	<refname>sd_journal_perror</refname>
976c46f8	51	<refname>SD_JOURNAL_SUPPRESS_LOCATION</refname>
a8eedf49 LP	52	<refpurpose>Submit log entries to the journal</refpurpose>
	53	</refnamediv>
	54
	55	<refsynopsisdiv>
	56	<funcsynopsis>
	57	<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
	58
	59	<funcprototype>
	60	<funcdef>int <function>sd_journal_print</function></funcdef>
	61	<paramdef>int <parameter>priority</parameter></paramdef>
	62	<paramdef>const char* <parameter>format</parameter></paramdef>
	63	<paramdef>...</paramdef>
	64	</funcprototype>
	65
	66	<funcprototype>
	67	<funcdef>int <function>sd_journal_printv</function></funcdef>
	68	<paramdef>int <parameter>priority</parameter></paramdef>
	69	<paramdef>const char* <parameter>format</parameter></paramdef>
	70	<paramdef>va_list <parameter>ap</parameter></paramdef>
	71	</funcprototype>
	72
	73	<funcprototype>
	74	<funcdef>int <function>sd_journal_send</function></funcdef>
	75	<paramdef>const char* <parameter>format</parameter></paramdef>
	76	<paramdef>...</paramdef>
	77	</funcprototype>
	78
	79	<funcprototype>
	80	<funcdef>int <function>sd_journal_sendv</function></funcdef>
	81	<paramdef>const struct iovec *<parameter>iov</parameter></paramdef>
	82	<paramdef>int <parameter>n</parameter></paramdef>
	83	</funcprototype>
	84
18c7ed18 LP	85	<funcprototype>
	86	<funcdef>int <function>sd_journal_perror</function></funcdef>
	87	<paramdef>const char* <parameter>message</parameter></paramdef>
	88	</funcprototype>
	89
a8eedf49 LP	90	</funcsynopsis>
	91	</refsynopsisdiv>
	92
	93	<refsect1>
	94	<title>Description</title>
	95
	96	<para><function>sd_journal_print()</function> may be
	97	used to submit simple, plain text log entries to the
	98	system journal. The first argument is a priority
	99	value. This is followed by a format string and its
	100	parameters, similar to
	101	<citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	102	or
	103	<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
	104	priority value is one of
74d00578 ZJS	105	<constant>LOG_EMERG</constant>,
	106	<constant>LOG_ALERT</constant>,
	107	<constant>LOG_CRIT</constant>,
	108	<constant>LOG_ERR</constant>,
	109	<constant>LOG_WARNING</constant>,
	110	<constant>LOG_NOTICE</constant>,
	111	<constant>LOG_INFO</constant>,
	112	<constant>LOG_DEBUG</constant>, as defined in
a8eedf49 LP	113	<filename>syslog.h</filename>, see
	114	<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	115	for details. It is recommended to use this call to
	116	submit log messages in the application locale or system
	117	locale and in UTF-8 format, but no such restrictions
	118	are enforced.</para>
	119
	120	<para><function>sd_journal_printv()</function> is
	121	similar to <function>sd_journal_print()</function> but
	122	takes a variable argument list encapsulated in an
74d00578	123	object of type <varname>va_list</varname> (see
a8eedf49 LP	124	<citerefentry><refentrytitle>stdarg</refentrytitle><manvolnum>3</manvolnum></citerefentry>
a8eedf49 LP	125	for more information) instead of the format string. It
c5315881	126	is otherwise equivalent in behavior.</para>
a8eedf49 LP	127
	128	<para><function>sd_journal_send()</function> may be
	129	used to submit structured log entries to the system
	130	journal. It takes a series of format strings, each
	131	immediately followed by their associated parameters,
74d00578	132	terminated by <constant>NULL</constant>. The strings passed should be of
a8eedf49	133	the format <literal>VARIABLE=value</literal>. The
bdfb9e7f LP	134	variable name must be in uppercase and consist only of
	135	characters, numbers and underscores, and may not begin
	136	with an underscore. (All assignments that do not
	137	follow this syntax will be ignored.) The value can be
	138	of any size and format. It is highly recommended to
	139	submit text strings formatted in the UTF-8 character
	140	encoding only, and submit binary fields only when
92fba83e	141	formatting in UTF-8 strings is not sensible. A number
bdfb9e7f	142	of well known fields are defined, see
a8eedf49 LP	143	<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
a8eedf49 LP	144	for details, but additional application defined fields
bdfb9e7f LP	145	may be used. A variable may be assigned more than one
bdfb9e7f LP	146	value per entry.</para>
a8eedf49 LP	147
	148	<para><function>sd_journal_sendv()</function> is
	149	similar to <function>sd_journal_send()</function> but
74d00578	150	takes an array of <varname>struct iovec</varname> (as
a8eedf49 LP	151	defined in <filename>uio.h</filename>, see
	152	<citerefentry><refentrytitle>readv</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	153	for details) instead of the format string. Each
	154	structure should reference one field of the entry to
	155	submit. The second argument specifies the number of
65b3903f ZJS	156	structures in the array.
65b3903f ZJS	157	<function>sd_journal_sendv()</function> is
a8eedf49 LP	158	particularly useful to submit binary objects to the
	159	journal where that is necessary.</para>
	160
18c7ed18 LP	161	<para><function>sd_journal_perror()</function> is a
	162	similar to
	163	<citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	164	and writes a message to the journal that consists of
	165	the passed string, suffixed with ": " and a human
	166	readable representation of the current error code
	167	stored in
	168	<citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
79640424	169	the message string is passed as <constant>NULL</constant> or empty string,
18c7ed18 LP	170	only the error string representation will be written,
	171	prefixed with nothing. An additional journal field
	172	ERRNO= is included in the entry containing the numeric
	173	error code formatted as decimal string. The log
74d00578	174	priority used is <constant>LOG_ERR</constant> (3).</para>
18c7ed18	175
a8eedf49	176	<para>Note that <function>sd_journal_send()</function>
19125c20	177	is a wrapper around
a8eedf49 LP	178	<function>sd_journal_sendv()</function> to make it
	179	easier to use when only text strings shall be
	180	submitted. Also, the following two calls are
	181	mostly equivalent:</para>
	182
	183	<programlisting>sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid());
	184
	185	sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(),
	186	"PRIORITY=%i", LOG_INFO,
	187	NULL);</programlisting>
	188
	189	<para>Note that these calls implicitly add fields for
	190	the source file, function name and code line where
	191	invoked. This is implemented with macros. If this is
79640424	192	not desired, it can be turned off by defining
a8eedf49 LP	193	SD_JOURNAL_SUPPRESS_LOCATION before including
a8eedf49 LP	194	<filename>sd-journal.h</filename>.</para>
6aae0ed2 LP	195
6aae0ed2 LP	196	<para><citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
bb31a4ac	197	and <function>sd_journal_print()</function> may
49f43d5f	198	largely be used interchangeably
6aae0ed2 LP	199	functionality-wise. However, note that log messages
	200	logged via the former take a different path to the
	201	journal server than the later, and hence global
	202	chronological ordering between the two streams cannot
	203	be guaranteed. Using
	204	<function>sd_journal_print()</function> has the
e9dd9f95	205	benefit of logging source code line, filenames, and
66f756d4	206	functions as metadata along all entries, and
6aae0ed2 LP	207	guaranteeing chronological ordering with structured
	208	log entries that are generated via
	209	<function>sd_journal_send()</function>. Using
	210	<function>syslog()</function> has the benefit of being
	211	more portable.</para>
a8eedf49 LP	212	</refsect1>
	213
	214	<refsect1>
	215	<title>Return Value</title>
	216
18c7ed18 LP	217	<para>The four calls return 0 on success or a negative
	218	errno-style error code. The
	219	<citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	220	variable itself is not altered.</para>
a8eedf49 LP	221	</refsect1>
a8eedf49 LP	222
65b3903f ZJS	223	<refsect1>
	224	<title>Async signal safety</title>
	225	<para><function>sd_journal_sendv()</function> is "async signal
	226	safe" in the meaning of <citerefentry><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
	227	</para>
	228
	229	<para><function>sd_journal_print</function>,
	230	<function>sd_journal_printv</function>,
	231	<function>sd_journal_send</function>, and
	232	<function>sd_journal_perror</function> are
	233	not async signal safe.</para>
	234	</refsect1>
	235
a8eedf49 LP	236	<refsect1>
	237	<title>Notes</title>
	238
	239	<para>The <function>sd_journal_print()</function>,
	240	<function>sd_journal_printv()</function>,
	241	<function>sd_journal_send()</function> and
	242	<function>sd_journal_sendv()</function> interfaces
494a6682	243	are available as a shared library, which can be compiled
a8eedf49	244	and linked to with the
14bf8788	245	<constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
a8eedf49 LP	246	file.</para>
	247	</refsect1>
	248
	249	<refsect1>
	250	<title>See Also</title>
	251
	252	<para>
	253	<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
cb07866b	254	<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
a8eedf49 LP	255	<citerefentry><refentrytitle>sd_journal_stream_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
a8eedf49 LP	256	<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
18c7ed18 LP	257	<citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
18c7ed18 LP	258	<citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
65b3903f ZJS	259	<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
	260	<citerefentry><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
	261	<citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
a8eedf49 LP	262	</para>
	263	</refsect1>
	264
	265	</refentry>