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

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

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  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
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<refentry id="sd_notify"
        xmlns:xi="http://www.w3.org/2001/XInclude">

        <refentryinfo>
                <title>sd_notify</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_notify</refentrytitle>
                <manvolnum>3</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd_notify</refname>
                <refname>sd_notifyf</refname>
                <refname>sd_pid_notify</refname>
                <refname>sd_pid_notifyf</refname>
                <refname>sd_pid_notify_with_fds</refname>
                <refpurpose>Notify service manager about start-up completion and other service status changes</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <funcsynopsis>
                        <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>

                        <funcprototype>
                                <funcdef>int <function>sd_notify</function></funcdef>
                                <paramdef>int <parameter>unset_environment</parameter></paramdef>
                                <paramdef>const char *<parameter>state</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_notifyf</function></funcdef>
                                <paramdef>int <parameter>unset_environment</parameter></paramdef>
                                <paramdef>const char *<parameter>format</parameter></paramdef>
                                <paramdef>...</paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_pid_notify</function></funcdef>
                                <paramdef>pid_t <parameter>pid</parameter></paramdef>
                                <paramdef>int <parameter>unset_environment</parameter></paramdef>
                                <paramdef>const char *<parameter>state</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_pid_notifyf</function></funcdef>
                                <paramdef>pid_t <parameter>pid</parameter></paramdef>
                                <paramdef>int <parameter>unset_environment</parameter></paramdef>
                                <paramdef>const char *<parameter>format</parameter></paramdef>
                                <paramdef>...</paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_pid_notify_with_fds</function></funcdef>
                                <paramdef>pid_t <parameter>pid</parameter></paramdef>
                                <paramdef>int <parameter>unset_environment</parameter></paramdef>
                                <paramdef>const char *<parameter>state</parameter></paramdef>
                                <paramdef>const int *<parameter>fds</parameter></paramdef>
                                <paramdef>unsigned <parameter>n_fds</parameter></paramdef>
                        </funcprototype>
                </funcsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>
                <para><function>sd_notify()</function> may be called
                by a service to notify the service manager about
                state changes. It can be used to send arbitrary
                information, encoded in an environment-block-like
                string. Most importantly it can be used for start-up
                completion notification.</para>

                <para>If the <parameter>unset_environment</parameter>
                parameter is non-zero, <function>sd_notify()</function>
                will unset the <varname>$NOTIFY_SOCKET</varname>
                environment variable before returning (regardless of
                whether the function call itself succeeded or
                not). Further calls to
                <function>sd_notify()</function> will then fail, but
                the variable is no longer inherited by child
                processes.</para>

                <para>The <parameter>state</parameter> parameter
                should contain a newline-separated list of variable
                assignments, similar in style to an environment
                block. A trailing newline is implied if none is
                specified. The string may contain any kind of variable
                assignments, but the following shall be considered
                well-known:</para>

                <variablelist>
                        <varlistentry>
                                <term>READY=1</term>

                                <listitem><para>Tells the service
                                manager that service startup is
                                finished. This is only used by systemd
                                if the service definition file has
                                Type=notify set. Since there is little
                                value in signaling non-readiness, the
                                only value services should send is
                                <literal>READY=1</literal>
                                (i.e. <literal>READY=0</literal> is
                                not defined).</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term>RELOADING=1</term>

                                <listitem><para>Tells the service manager
                                that the service is reloading its
                                configuration. This is useful to allow
                                the service manager to track the service's
                                internal state, and present it to the
                                user. Note that a service that sends
                                this notification must also send a
                                <literal>READY=1</literal>
                                notification when it completed
                                reloading its
                                configuration.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term>STOPPING=1</term>

                                <listitem><para>Tells the service manager
                                that the service is beginning its
                                shutdown. This is useful to allow the
                                service manager to track the service's
                                internal state, and present it to the
                                user.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term>STATUS=...</term>

                                <listitem><para>Passes a single-line
                                UTF-8 status string back to the service manager
                                that describes the service state. This
                                is free-form and can be used for
                                various purposes: general state
                                feedback, fsck-like programs could
                                pass completion percentages and
                                failing programs could pass a human
                                readable error message. Example:
                                <literal>STATUS=Completed 66% of file
                                system
                                check...</literal></para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term>ERRNO=...</term>

                                <listitem><para>If a service fails, the
                                errno-style error code, formatted as
                                string. Example: <literal>ERRNO=2</literal> for
                                ENOENT.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term>BUSERROR=...</term>

                                <listitem><para>If a service fails, the
                                D-Bus error-style error code. Example:
                                <literal>BUSERROR=org.freedesktop.DBus.Error.TimedOut</literal></para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term>MAINPID=...</term>

                                <listitem><para>The main process ID (PID) of the
                                service, in case the service manager did
                                not fork off the process
                                itself. Example:
                                <literal>MAINPID=4711</literal></para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term>WATCHDOG=1</term>

                                <listitem><para>Tells the service manager to
                                update the watchdog timestamp. This is
                                the keep-alive ping that services need
                                to issue in regular intervals if
                                <varname>WatchdogSec=</varname> is
                                enabled for it. See
                                <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                                for information how to enable this
                                functionality and
                                <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                                for the details of how the service can
                                check if the the watchdog is enabled.
                                </para></listitem>
                        </varlistentry>


                        <varlistentry>
                                <term>FDSTORE=1</term>

                                <listitem><para>Stores additional file
                                descriptors in the service
                                manager. File descriptors sent this
                                way will be maintained per-service by
                                the service manager and be passed
                                again using the usual file descriptor
                                passing logic on the next invocation
                                of the service (see
                                <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>). This
                                is useful for implementing service
                                restart schemes where services
                                serialize their state to
                                <filename>/run</filename>, push their
                                file descriptors to the system
                                manager, and are then restarted,
                                retrieving their state again via
                                socket passing and
                                <filename>/run</filename>. Note that
                                the service manager will accept
                                messages for a service only if
                                <varname>FileDescriptorStoreMax=</varname>
                                is set to non-zero for it (defaults to
                                zero). See
                                <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                                for details. Multiple arrays of file
                                descriptors may be sent in separate
                                messages, in which case the arrays are
                                combined. Note that the service
                                manager removes duplicate file
                                descriptors before passing them to the
                                service. Use
                                <function>sd_pid_notify_with_fds()</function>
                                to send messages with
                                <literal>FDSTORE=1</literal>, see
                                below.</para></listitem>
                        </varlistentry>

                </variablelist>

                <para>It is recommended to prefix variable names that
                are not listed above with <varname>X_</varname> to
                avoid namespace clashes.</para>

                <para>Note that systemd will accept status data sent
                from a service only if the
                <varname>NotifyAccess=</varname> option is correctly
                set in the service definition file. See
                <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                for details.</para>

                <para><function>sd_notifyf()</function> is similar to
                <function>sd_notify()</function> but takes a
                <function>printf()</function>-like format string plus
                arguments.</para>

                <para><function>sd_pid_notify()</function> and
                <function>sd_pid_notifyf()</function> are similar to
                <function>sd_notify()</function> and
                <function>sd_notifyf()</function> but take a process
                ID (PID) to use as originating PID for the message as
                first argument. This is useful to send notification
                messages on behalf of other processes, provided the
                appropriate privileges are available. If the PID
                argument is specified as 0 the process ID of the
                calling process is used, in which case the calls are
                fully equivalent to <function>sd_notify()</function>
                and <function>sd_notifyf()</function>.</para>

                <para><function>sd_pid_notify_with_fds()</function> is
                similar to <function>sd_pid_notify()</function> but
                takes an additional array of file descriptors. These
                file descriptors are sent along the notification
                message to the service manager. This is particularly
                useful for sending <literal>FDSTORE=1</literal>
                messages, as described above. The additional arguments
                are a pointer to the file descriptor array plus the
                number of file descriptors in the array. If the number
                of file descriptors is passed as 0, the call is fully
                equivalent to <function>sd_pid_notify()</function>,
                i.e. no file descriptors are passed. Note that sending
                file descriptors to the service manager on messages
                that do not expect them (i.e. without
                <literal>FDSTORE=1</literal>) they are immediately
                closed on reception.</para>
        </refsect1>

        <refsect1>
                <title>Return Value</title>

                <para>On failure, these calls return a negative
                errno-style error code. If
                <varname>$NOTIFY_SOCKET</varname> was not set and
                hence no status data could be sent, 0 is returned. If
                the status was sent, these functions return with a
                positive return value. In order to support both, init
                systems that implement this scheme and those which
                do not, it is generally recommended to ignore the return
                value of this call.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>

                <para>Internally, these functions send a single
                datagram with the state string as payload to the
                <constant>AF_UNIX</constant> socket referenced in the
                <varname>$NOTIFY_SOCKET</varname> environment
                variable. If the first character of
                <varname>$NOTIFY_SOCKET</varname> is <literal>@</literal>, the string is
                understood as Linux abstract namespace socket. The
                datagram is accompanied by the process credentials of
                the sending service, using SCM_CREDENTIALS.</para>
        </refsect1>

        <refsect1>
                <title>Environment</title>

                <variablelist class='environment-variables'>
                        <varlistentry>
                                <term><varname>$NOTIFY_SOCKET</varname></term>

                                <listitem><para>Set by the service manager
                                for supervised processes for status
                                and start-up completion
                                notification. This environment variable
                                specifies the socket
                                <function>sd_notify()</function> talks
                                to. See above for details.</para></listitem>
                        </varlistentry>
                </variablelist>
        </refsect1>

        <refsect1>
                <title>Examples</title>

                <example>
                        <title>Start-up Notification</title>

                        <para>When a service finished starting up, it
                        might issue the following call to notify
                        the service manager:</para>

                        <programlisting>sd_notify(0, "READY=1");</programlisting>
                </example>

                <example>
                        <title>Extended Start-up Notification</title>

                        <para>A service could send the following after
                        completing initialization:</para>

                        <programlisting>sd_notifyf(0, "READY=1\n"
              "STATUS=Processing requests...\n"
              "MAINPID=%lu",
              (unsigned long) getpid());</programlisting>
                </example>

                <example>
                        <title>Error Cause Notification</title>

                        <para>A service could send the following shortly before exiting, on failure:</para>

                        <programlisting>sd_notifyf(0, "STATUS=Failed to start up: %s\n"
              "ERRNO=%i",
              strerror(errno),
              errno);</programlisting>
                </example>

                <example>
                        <title>Store a File Descriptor in the Service Manager</title>

                        <para>To store an open file descriptor in the
                        service manager, in order to continue
                        operation after a service restart without
                        losing state use
                        <literal>FDSTORE=1</literal>:</para>

                        <programlisting>sd_pid_notify_with_fds(0, 0, "FDSTORE=1", &amp;fd, 1);</programlisting>
                </example>
        </refsect1>

        <refsect1>
                <title>See Also</title>
                <para>
                        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>
Commit	Line	Data
f9378423 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 2010 Lennart Poettering
	9
	10	systemd is free software; you can redistribute it and/or modify it
5430f7f2 LP	11	under the terms of the GNU Lesser General Public License as published by
5430f7f2 LP	12	the Free Software Foundation; either version 2.1 of the License, or
f9378423 LP	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
5430f7f2	18	Lesser General Public License for more details.
f9378423	19
5430f7f2	20	You should have received a copy of the GNU Lesser General Public License
f9378423 LP	21	along with systemd; If not, see <http://www.gnu.org/licenses/>.
	22	-->
	23
6a70f3aa ZJS	24	<refentry id="sd_notify"
6a70f3aa ZJS	25	xmlns:xi="http://www.w3.org/2001/XInclude">
f9378423 LP	26
	27	<refentryinfo>
	28	<title>sd_notify</title>
	29	<productname>systemd</productname>
	30
	31	<authorgroup>
	32	<author>
	33	<contrib>Developer</contrib>
	34	<firstname>Lennart</firstname>
	35	<surname>Poettering</surname>
	36	<email>lennart@poettering.net</email>
	37	</author>
	38	</authorgroup>
	39	</refentryinfo>
	40
	41	<refmeta>
	42	<refentrytitle>sd_notify</refentrytitle>
	43	<manvolnum>3</manvolnum>
	44	</refmeta>
	45
	46	<refnamediv>
	47	<refname>sd_notify</refname>
	48	<refname>sd_notifyf</refname>
a354329f LP	49	<refname>sd_pid_notify</refname>
	50	<refname>sd_pid_notifyf</refname>
	51	<refname>sd_pid_notify_with_fds</refname>
308d72dc	52	<refpurpose>Notify service manager about start-up completion and other service status changes</refpurpose>
f9378423 LP	53	</refnamediv>
	54
	55	<refsynopsisdiv>
	56	<funcsynopsis>
a822cbfa	57	<funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo>
f9378423 LP	58
	59	<funcprototype>
	60	<funcdef>int <function>sd_notify</function></funcdef>
	61	<paramdef>int <parameter>unset_environment</parameter></paramdef>
	62	<paramdef>const char *<parameter>state</parameter></paramdef>
	63	</funcprototype>
	64
	65	<funcprototype>
	66	<funcdef>int <function>sd_notifyf</function></funcdef>
	67	<paramdef>int <parameter>unset_environment</parameter></paramdef>
	68	<paramdef>const char *<parameter>format</parameter></paramdef>
	69	<paramdef>...</paramdef>
	70	</funcprototype>
a354329f LP	71
	72	<funcprototype>
	73	<funcdef>int <function>sd_pid_notify</function></funcdef>
	74	<paramdef>pid_t <parameter>pid</parameter></paramdef>
	75	<paramdef>int <parameter>unset_environment</parameter></paramdef>
	76	<paramdef>const char *<parameter>state</parameter></paramdef>
	77	</funcprototype>
	78
	79	<funcprototype>
	80	<funcdef>int <function>sd_pid_notifyf</function></funcdef>
	81	<paramdef>pid_t <parameter>pid</parameter></paramdef>
	82	<paramdef>int <parameter>unset_environment</parameter></paramdef>
	83	<paramdef>const char *<parameter>format</parameter></paramdef>
	84	<paramdef>...</paramdef>
	85	</funcprototype>
	86
	87	<funcprototype>
	88	<funcdef>int <function>sd_pid_notify_with_fds</function></funcdef>
	89	<paramdef>pid_t <parameter>pid</parameter></paramdef>
	90	<paramdef>int <parameter>unset_environment</parameter></paramdef>
	91	<paramdef>const char *<parameter>state</parameter></paramdef>
	92	<paramdef>const int *<parameter>fds</parameter></paramdef>
	93	<paramdef>unsigned <parameter>n_fds</parameter></paramdef>
	94	</funcprototype>
f9378423 LP	95	</funcsynopsis>
	96	</refsynopsisdiv>
	97
	98	<refsect1>
	99	<title>Description</title>
308d72dc LP	100	<para><function>sd_notify()</function> may be called
	101	by a service to notify the service manager about
	102	state changes. It can be used to send arbitrary
	103	information, encoded in an environment-block-like
	104	string. Most importantly it can be used for start-up
	105	completion notification.</para>
f9378423 LP	106
f9378423 LP	107	<para>If the <parameter>unset_environment</parameter>
79640424	108	parameter is non-zero, <function>sd_notify()</function>
f9378423	109	will unset the <varname>$NOTIFY_SOCKET</varname>
494a6682	110	environment variable before returning (regardless of
f9378423 LP	111	whether the function call itself succeeded or
	112	not). Further calls to
	113	<function>sd_notify()</function> will then fail, but
	114	the variable is no longer inherited by child
	115	processes.</para>
	116
	117	<para>The <parameter>state</parameter> parameter
bb31a4ac	118	should contain a newline-separated list of variable
f9378423 LP	119	assignments, similar in style to an environment
	120	block. A trailing newline is implied if none is
	121	specified. The string may contain any kind of variable
	122	assignments, but the following shall be considered
	123	well-known:</para>
	124
	125	<variablelist>
	126	<varlistentry>
	127	<term>READY=1</term>
	128
308d72dc LP	129	<listitem><para>Tells the service
	130	manager that service startup is
	131	finished. This is only used by systemd
	132	if the service definition file has
	133	Type=notify set. Since there is little
bb31a4ac	134	value in signaling non-readiness, the
308d72dc LP	135	only value services should send is
	136	<literal>READY=1</literal>
	137	(i.e. <literal>READY=0</literal> is
	138	not defined).</para></listitem>
	139	</varlistentry>
	140
	141	<varlistentry>
	142	<term>RELOADING=1</term>
	143
	144	<listitem><para>Tells the service manager
	145	that the service is reloading its
	146	configuration. This is useful to allow
	147	the service manager to track the service's
	148	internal state, and present it to the
	149	user. Note that a service that sends
	150	this notification must also send a
	151	<literal>READY=1</literal>
	152	notification when it completed
	153	reloading its
	154	configuration.</para></listitem>
	155	</varlistentry>
	156
	157	<varlistentry>
	158	<term>STOPPING=1</term>
	159
	160	<listitem><para>Tells the service manager
	161	that the service is beginning its
	162	shutdown. This is useful to allow the
	163	service manager to track the service's
	164	internal state, and present it to the
	165	user.</para></listitem>
f9378423 LP	166	</varlistentry>
	167
	168	<varlistentry>
	169	<term>STATUS=...</term>
	170
	171	<listitem><para>Passes a single-line
308d72dc LP	172	UTF-8 status string back to the service manager
308d72dc LP	173	that describes the service state. This
af62c704	174	is free-form and can be used for
f9378423 LP	175	various purposes: general state
	176	feedback, fsck-like programs could
	177	pass completion percentages and
	178	failing programs could pass a human
	179	readable error message. Example:
308d72dc LP	180	<literal>STATUS=Completed 66% of file
	181	system
	182	check...</literal></para></listitem>
f9378423 LP	183	</varlistentry>
	184
	185	<varlistentry>
	186	<term>ERRNO=...</term>
	187
308d72dc	188	<listitem><para>If a service fails, the
f9378423	189	errno-style error code, formatted as
308d72dc	190	string. Example: <literal>ERRNO=2</literal> for
f9378423 LP	191	ENOENT.</para></listitem>
	192	</varlistentry>
	193
	194	<varlistentry>
	195	<term>BUSERROR=...</term>
	196
308d72dc	197	<listitem><para>If a service fails, the
f9378423	198	D-Bus error-style error code. Example:
308d72dc	199	<literal>BUSERROR=org.freedesktop.DBus.Error.TimedOut</literal></para></listitem>
f9378423 LP	200	</varlistentry>
	201
	202	<varlistentry>
	203	<term>MAINPID=...</term>
	204
a354329f	205	<listitem><para>The main process ID (PID) of the
308d72dc	206	service, in case the service manager did
f9378423 LP	207	not fork off the process
f9378423 LP	208	itself. Example:
308d72dc	209	<literal>MAINPID=4711</literal></para></listitem>
f9378423	210	</varlistentry>
a6927d7f MO	211
	212	<varlistentry>
	213	<term>WATCHDOG=1</term>
	214
a354329f	215	<listitem><para>Tells the service manager to
dac051ad LP	216	update the watchdog timestamp. This is
	217	the keep-alive ping that services need
	218	to issue in regular intervals if
	219	<varname>WatchdogSec=</varname> is
	220	enabled for it. See
	221	<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
a9becdd6 ZJS	222	for information how to enable this
a9becdd6 ZJS	223	functionality and
09812eb7	224	<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
a9becdd6 ZJS	225	for the details of how the service can
	226	check if the the watchdog is enabled.
	227	</para></listitem>
a6927d7f	228	</varlistentry>
a354329f LP	229
	230
	231	<varlistentry>
	232	<term>FDSTORE=1</term>
	233
	234	<listitem><para>Stores additional file
	235	descriptors in the service
	236	manager. File descriptors sent this
	237	way will be maintained per-service by
	238	the service manager and be passed
	239	again using the usual file descriptor
	240	passing logic on the next invocation
	241	of the service (see
	242	<citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>). This
	243	is useful for implementing service
	244	restart schemes where services
	245	serialize their state to
	246	<filename>/run</filename>, push their
	247	file descriptors to the system
	248	manager, and are then restarted,
	249	retrieving their state again via
	250	socket passing and
	251	<filename>/run</filename>. Note that
	252	the service manager will accept
	253	messages for a service only if
	254	<varname>FileDescriptorStoreMax=</varname>
	255	is set to non-zero for it (defaults to
	256	zero). See
	257	<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
	258	for details. Multiple arrays of file
cc98b302	259	descriptors may be sent in separate
a354329f LP	260	messages, in which case the arrays are
	261	combined. Note that the service
	262	manager removes duplicate file
	263	descriptors before passing them to the
	264	service. Use
	265	<function>sd_pid_notify_with_fds()</function>
	266	to send messages with
	267	<literal>FDSTORE=1</literal>, see
	268	below.</para></listitem>
	269	</varlistentry>
	270
f9378423 LP	271	</variablelist>
f9378423 LP	272
436c44a5	273	<para>It is recommended to prefix variable names that
a354329f LP	274	are not listed above with <varname>X_</varname> to
a354329f LP	275	avoid namespace clashes.</para>
f9378423 LP	276
f9378423 LP	277	<para>Note that systemd will accept status data sent
308d72dc	278	from a service only if the
f9378423 LP	279	<varname>NotifyAccess=</varname> option is correctly
	280	set in the service definition file. See
	281	<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
	282	for details.</para>
	283
	284	<para><function>sd_notifyf()</function> is similar to
9f846242	285	<function>sd_notify()</function> but takes a
f9378423 LP	286	<function>printf()</function>-like format string plus
f9378423 LP	287	arguments.</para>
a354329f LP	288
	289	<para><function>sd_pid_notify()</function> and
	290	<function>sd_pid_notifyf()</function> are similar to
	291	<function>sd_notify()</function> and
	292	<function>sd_notifyf()</function> but take a process
	293	ID (PID) to use as originating PID for the message as
	294	first argument. This is useful to send notification
	295	messages on behalf of other processes, provided the
	296	appropriate privileges are available. If the PID
	297	argument is specified as 0 the process ID of the
	298	calling process is used, in which case the calls are
	299	fully equivalent to <function>sd_notify()</function>
	300	and <function>sd_notifyf()</function>.</para>
	301
	302	<para><function>sd_pid_notify_with_fds()</function> is
	303	similar to <function>sd_pid_notify()</function> but
	304	takes an additional array of file descriptors. These
	305	file descriptors are sent along the notification
	306	message to the service manager. This is particularly
	307	useful for sending <literal>FDSTORE=1</literal>
	308	messages, as described above. The additional arguments
	309	are a pointer to the file descriptor array plus the
	310	number of file descriptors in the array. If the number
	311	of file descriptors is passed as 0, the call is fully
	312	equivalent to <function>sd_pid_notify()</function>,
	313	i.e. no file descriptors are passed. Note that sending
	314	file descriptors to the service manager on messages
	315	that do not expect them (i.e. without
	316	<literal>FDSTORE=1</literal>) they are immediately
	317	closed on reception.</para>
f9378423 LP	318	</refsect1>
	319
	320	<refsect1>
	321	<title>Return Value</title>
	322
	323	<para>On failure, these calls return a negative
	324	errno-style error code. If
	325	<varname>$NOTIFY_SOCKET</varname> was not set and
af62c704	326	hence no status data could be sent, 0 is returned. If
79640424	327	the status was sent, these functions return with a
af62c704	328	positive return value. In order to support both, init
f9378423	329	systems that implement this scheme and those which
6b4991cf	330	do not, it is generally recommended to ignore the return
f9378423 LP	331	value of this call.</para>
	332	</refsect1>
	333
	334	<refsect1>
	335	<title>Notes</title>
	336
6a70f3aa	337	<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
f9378423 LP	338
	339	<para>Internally, these functions send a single
	340	datagram with the state string as payload to the
74d00578	341	<constant>AF_UNIX</constant> socket referenced in the
f9378423 LP	342	<varname>$NOTIFY_SOCKET</varname> environment
f9378423 LP	343	variable. If the first character of
79640424	344	<varname>$NOTIFY_SOCKET</varname> is <literal>@</literal>, the string is
f9378423 LP	345	understood as Linux abstract namespace socket. The
f9378423 LP	346	datagram is accompanied by the process credentials of
308d72dc	347	the sending service, using SCM_CREDENTIALS.</para>
f9378423 LP	348	</refsect1>
f9378423 LP	349
7874bcd6 LP	350	<refsect1>
	351	<title>Environment</title>
	352
ccc9a4f9	353	<variablelist class='environment-variables'>
7874bcd6 LP	354	<varlistentry>
	355	<term><varname>$NOTIFY_SOCKET</varname></term>
	356
308d72dc	357	<listitem><para>Set by the service manager
7874bcd6 LP	358	for supervised processes for status
	359	and start-up completion
	360	notification. This environment variable
	361	specifies the socket
	362	<function>sd_notify()</function> talks
	363	to. See above for details.</para></listitem>
	364	</varlistentry>
	365	</variablelist>
	366	</refsect1>
	367
f9378423 LP	368	<refsect1>
	369	<title>Examples</title>
	370
	371	<example>
	372	<title>Start-up Notification</title>
	373
308d72dc	374	<para>When a service finished starting up, it
ad678a06	375	might issue the following call to notify
308d72dc	376	the service manager:</para>
f9378423 LP	377
	378	<programlisting>sd_notify(0, "READY=1");</programlisting>
	379	</example>
	380
	381	<example>
	382	<title>Extended Start-up Notification</title>
	383
308d72dc	384	<para>A service could send the following after
f9378423 LP	385	completing initialization:</para>
	386
	387	<programlisting>sd_notifyf(0, "READY=1\n"
	388	"STATUS=Processing requests...\n"
	389	"MAINPID=%lu",
	390	(unsigned long) getpid());</programlisting>
	391	</example>
	392
	393	<example>
	394	<title>Error Cause Notification</title>
	395
a354329f	396	<para>A service could send the following shortly before exiting, on failure:</para>
f9378423 LP	397
	398	<programlisting>sd_notifyf(0, "STATUS=Failed to start up: %s\n"
	399	"ERRNO=%i",
	400	strerror(errno),
	401	errno);</programlisting>
	402	</example>
a354329f LP	403
	404	<example>
	405	<title>Store a File Descriptor in the Service Manager</title>
	406
	407	<para>To store an open file descriptor in the
	408	service manager, in order to continue
	409	operation after a service restart without
	410	losing state use
	411	<literal>FDSTORE=1</literal>:</para>
	412
	413	<programlisting>sd_pid_notify_with_fds(0, 0, "FDSTORE=1", &fd, 1);</programlisting>
	414	</example>
f9378423 LP	415	</refsect1>
	416
	417	<refsect1>
	418	<title>See Also</title>
	419	<para>
160cd5c9	420	<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
cb07866b	421	<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
f9378423	422	<citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
09812eb7 LP	423	<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
09812eb7 LP	424	<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
f9378423 LP	425	</para>
	426	</refsect1>
	427
	428	</refentry>