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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 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<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 <systemd/sd-login.h></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>
|
