<?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 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-login" conditional='HAVE_PAM' xmlns:xi="http://www.w3.org/2001/XInclude"> <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>3</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</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 <constant>NULL</constant> terminated and need to be freed by the caller with the libc <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry> call after use, including the strings referenced therein. Similarly, individual strings returned need to be freed, as well.</para> <para>As a special exception, instead of an empty string array <constant>NULL</constant> 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> <xi:include href="libsystemd-pkgconfig.xml" /> <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>3</manvolnum></citerefentry>, <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> </para> </refsect1> </refentry>