[thirdparty/systemd.git] / man / sd-login.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">

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  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
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  the Free Software Foundation; either version 2.1 of the License, or
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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-login">

        <refentryinfo>
                <title>sd-login</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-login</refentrytitle>
                <manvolnum>7</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd-login</refname>
                <refpurpose>APIs for
                tracking logins</refpurpose>
        </refnamediv>

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

                <cmdsynopsis>
                        <command>pkg-config --cflags --libs libsystemd-login</command>
                </cmdsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><filename>sd-login.h</filename> provides APIs to
                introspect and monitor seat, login session and user
                status information on the local system. </para>

                <para>See <ulink
                url="http://www.freedesktop.org/wiki/Software/systemd/multiseat">Multi-Seat
                on Linux</ulink> for an introduction into multi-seat
                support on Linux, the background for this set of APIs.</para>

                <para>Note that these APIs only allow purely passive access
                and monitoring of seats, sessions and users. To
                actively make changes to the seat configuration,
                terminate login sessions, or switch session on a seat
                you need to utilize the D-Bus API of
                systemd-logind, instead.</para>

                <para>These functions synchronously access data in
                <filename>/proc</filename>,
                <filename>/sys/fs/cgroup</filename> and
                <filename>/run</filename>. All of these are virtual
                file systems, hence the runtime cost of the accesses
                is relatively cheap.</para>

                <para>It is possible (and often a very good choice) to
                mix calls to the synchronous interface of
                <filename>sd-login.h</filename> with the asynchronous
                D-Bus interface of systemd-logind. However, if this is
                done you need to think a bit about possible races
                since the stream of events from D-Bus and from
                <filename>sd-login.h</filename> interfaces such as the
                login monitor are asynchronous and not ordered against
                each other.</para>

                <para>If the functions return string arrays, these are
                generally NULL terminated and need to be freed by the
                caller with the libc
                <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                call after use, including the strings referenced
                therein. Similar, individual strings returned need to
                be freed, as well.</para>

                <para>As a special exception, instead of an empty
                string array NULL may be returned, which should be
                treated equivalent to an empty string array.</para>

                <para>See
                <citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                for more information about the functions
                implemented.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>These APIs are implemented as shared library,
                which can be compiled and linked to with the
                <literal>libsystemd-login</literal>
                <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_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd-readahead</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>
Commit	Line	Data
01448ff9 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
01448ff9 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.
01448ff9	19
5430f7f2	20	You should have received a copy of the GNU Lesser General Public License
01448ff9 LP	21	along with systemd; If not, see <http://www.gnu.org/licenses/>.
	22	-->
	23
	24	<refentry id="sd-login">
	25
	26	<refentryinfo>
	27	<title>sd-login</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-login</refentrytitle>
	42	<manvolnum>7</manvolnum>
	43	</refmeta>
	44
	45	<refnamediv>
	46	<refname>sd-login</refname>
	47	<refpurpose>APIs for
	48	tracking logins</refpurpose>
	49	</refnamediv>
	50
	51	<refsynopsisdiv>
	52	<funcsynopsis>
	53	<funcsynopsisinfo>#include <systemd/sd-login.h></funcsynopsisinfo>
	54	</funcsynopsis>
	55
	56	<cmdsynopsis>
	57	<command>pkg-config --cflags --libs libsystemd-login</command>
	58	</cmdsynopsis>
	59	</refsynopsisdiv>
	60
	61	<refsect1>
	62	<title>Description</title>
	63
	64	<para><filename>sd-login.h</filename> provides APIs to
	65	introspect and monitor seat, login session and user
	66	status information on the local system. </para>
	67
	68	<para>See <ulink
	69	url="http://www.freedesktop.org/wiki/Software/systemd/multiseat">Multi-Seat
	70	on Linux</ulink> for an introduction into multi-seat
	71	support on Linux, the background for this set of APIs.</para>
	72
	73	<para>Note that these APIs only allow purely passive access
	74	and monitoring of seats, sessions and users. To
	75	actively make changes to the seat configuration,
	76	terminate login sessions, or switch session on a seat
	77	you need to utilize the D-Bus API of
595aae37 LP	78	systemd-logind, instead.</para>
595aae37 LP	79
5079a105	80	<para>These functions synchronously access data in
595aae37 LP	81	<filename>/proc</filename>,
	82	<filename>/sys/fs/cgroup</filename> and
	83	<filename>/run</filename>. All of these are virtual
	84	file systems, hence the runtime cost of the accesses
	85	is relatively cheap.</para>
	86
5079a105 LP	87	<para>It is possible (and often a very good choice) to
	88	mix calls to the synchronous interface of
	89	<filename>sd-login.h</filename> with the asynchronous
	90	D-Bus interface of systemd-logind. However, if this is
	91	done you need to think a bit about possible races
	92	since the stream of events from D-Bus and from
	93	<filename>sd-login.h</filename> interfaces such as the
	94	login monitor are asynchronous and not ordered against
	95	each other.</para>
	96
595aae37 LP	97	<para>If the functions return string arrays, these are
	98	generally NULL terminated and need to be freed by the
	99	caller with the libc
	100	<citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	101	call after use, including the strings referenced
	102	therein. Similar, individual strings returned need to
	103	be freed, as well.</para>
	104
	105	<para>As a special exception, instead of an empty
	106	string array NULL may be returned, which should be
	107	treated equivalent to an empty string array.</para>
01448ff9 LP	108
	109	<para>See
	110	<citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	111	<citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	112	<citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	113	<citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	114	<citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	115	<citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	116	for more information about the functions
	117	implemented.</para>
	118	</refsect1>
	119
	120	<refsect1>
	121	<title>Notes</title>
	122
	123	<para>These APIs are implemented as shared library,
	124	which can be compiled and linked to with the
	125	<literal>libsystemd-login</literal>
	126	<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
	127	file.</para>
	128	</refsect1>
	129
	130	<refsect1>
	131	<title>See Also</title>
	132	<para>
	133	<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
	134	<citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	135	<citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	136	<citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	137	<citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	138	<citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	139	<citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	140	<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
	141	<citerefentry><refentrytitle>sd-readahead</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
	142	<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
	143	</para>
	144	</refsect1>
	145
	146	</refentry>