147 lines
7.1 KiB
XML
147 lines
7.1 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd-login">
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<refentryinfo>
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<title>sd-login</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd-login</refentrytitle>
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<manvolnum>7</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd-login</refname>
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<refpurpose>APIs for
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tracking logins</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-login.h></funcsynopsisinfo>
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</funcsynopsis>
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<cmdsynopsis>
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<command>pkg-config --cflags --libs libsystemd-login</command>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>sd-login.h</filename> provides APIs to
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introspect and monitor seat, login session and user
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status information on the local system. </para>
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<para>See <ulink
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url="http://www.freedesktop.org/wiki/Software/systemd/multiseat">Multi-Seat
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on Linux</ulink> for an introduction into multi-seat
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support on Linux, the background for this set of APIs.</para>
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<para>Note that these APIs only allow purely passive access
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and monitoring of seats, sessions and users. To
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actively make changes to the seat configuration,
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terminate login sessions, or switch session on a seat
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you need to utilize the D-Bus API of
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systemd-logind, instead.</para>
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<para>These functions synchronously access data in
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<filename>/proc</filename>,
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<filename>/sys/fs/cgroup</filename> and
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<filename>/run</filename>. All of these are virtual
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file systems, hence the runtime cost of the accesses
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is relatively cheap.</para>
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<para>It is possible (and often a very good choice) to
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mix calls to the synchronous interface of
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<filename>sd-login.h</filename> with the asynchronous
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D-Bus interface of systemd-logind. However, if this is
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done you need to think a bit about possible races
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since the stream of events from D-Bus and from
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<filename>sd-login.h</filename> interfaces such as the
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login monitor are asynchronous and not ordered against
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each other.</para>
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<para>If the functions return string arrays, these are
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generally NULL terminated and need to be freed by the
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caller with the libc
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<citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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call after use, including the strings referenced
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therein. Similar, individual strings returned need to
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be freed, as well.</para>
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<para>As a special exception, instead of an empty
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string array NULL may be returned, which should be
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treated equivalent to an empty string array.</para>
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<para>See
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<citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for more information about the functions
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implemented.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>These APIs are implemented as shared library,
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which can be compiled and linked to with the
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<literal>libsystemd-login</literal>
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<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-readahead</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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