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247 lines
12 KiB
XML
247 lines
12 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_monitor_new" conditional='HAVE_PAM'>
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<refentryinfo>
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<title>sd_login_monitor_new</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_monitor_new</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_login_monitor_new</refname>
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<refname>sd_login_monitor_unref</refname>
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<refname>sd_login_monitor_flush</refname>
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<refname>sd_login_monitor_get_fd</refname>
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<refname>sd_login_monitor_get_events</refname>
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<refname>sd_login_monitor_get_timeout</refname>
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<refname>sd_login_monitor</refname>
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<refpurpose>Monitor login sessions, seats, users and virtual machines/containers</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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<funcprototype>
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<funcdef>int <function>sd_login_monitor_new</function></funcdef>
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<paramdef>const char* <parameter>category</parameter></paramdef>
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<paramdef>sd_login_monitor** <parameter>ret</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_login_monitor* <function>sd_login_monitor_unref</function></funcdef>
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<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_login_monitor_flush</function></funcdef>
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<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_login_monitor_get_fd</function></funcdef>
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<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_login_monitor_get_events</function></funcdef>
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<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_login_monitor_get_timeout</function></funcdef>
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<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
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<paramdef>uint64_t* <parameter>timeout_usec</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_login_monitor_new()</function> may
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be used to monitor login sessions, users, seats, and
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virtual machines/containers. Via a monitor object a
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file descriptor can be integrated into an application
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defined event loop which is woken up each time a user
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logs in, logs out or a seat is added or removed, or a
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session, user, seat or virtual machine/container
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changes state otherwise. The first parameter takes a
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string which can be <literal>seat</literal> (to get
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only notifications about seats being added, removed or
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changed), <literal>session</literal> (to get only
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notifications about sessions being created or removed
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or changed), <literal>uid</literal> (to get only
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notifications when a user changes state in respect to
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logins) or <literal>machine</literal> (to get only
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notifications when a virtual machine or container is
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started or stopped). If notifications shall be
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generated in all these conditions, NULL may be
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passed. Note that in the future additional categories
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may be defined. The second parameter returns a monitor
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object and needs to be freed with the
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<function>sd_login_monitor_unref()</function> call
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after use.</para>
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<para><function>sd_login_monitor_unref()</function>
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may be used to destroy a monitor object. Note that
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this will invalidate any file descriptor returned by
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<function>sd_login_monitor_get_fd()</function>.</para>
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<para><function>sd_login_monitor_flush()</function>
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may be used to reset the wakeup state of the monitor
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object. Whenever an event causes the monitor to wake
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up the event loop via the file descriptor this
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function needs to be called to reset the wake-up
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state. If this call is not invoked the file descriptor
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will immediately wake up the event loop again.</para>
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<para><function>sd_login_monitor_get_fd()</function>
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may be used to retrieve the file descriptor of the
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monitor object that may be integrated in an
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application defined event loop, based around
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<citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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or a similar interface. The application should include
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the returned file descriptor as wake-up source for the
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events mask returned by
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<function>sd_login_monitor_get_events()</function>. It
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should pass a timeout value as returned by
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<function>sd_login_monitor_get_timeout()</function>. Whenever
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a wake-up is triggered the file descriptor needs to be
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reset via
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<function>sd_login_monitor_flush()</function>. An
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application needs to reread the login state with a
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function like
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<citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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or similar to determine what changed.</para>
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<para><function>sd_login_monitor_get_events()</function>
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will return the <function>poll()</function> mask to
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wait for. This function will return a combination of
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<literal>POLLIN</literal>, <literal>POLLOUT</literal>
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and similar to fill into the
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<literal>.events</literal> field of <literal>struct
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pollfd</literal>.</para>
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<para><function>sd_login_monitor_get_timeout()</function>
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will return a timeout value for usage in
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<function>poll()</function>. This returns a value in
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microseconds since the epoch of CLOCK_MONOTONIC for
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timing out <function>poll()</function> in
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<literal>timeout_usec</literal>. See
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<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details about
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<literal>CLOCK_MONOTONIC</literal>. If there's no
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timeout to wait for this will fill in
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<literal>(uint64_t) -1</literal> instead. Note that
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<function>poll()</function> takes a relative timeout
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in milliseconds rather than an absolute timeout in
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microseconds. To convert the absolute 'us' timeout into
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relative 'ms', use code like the following:</para>
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<programlisting>uint64_t t;
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int msec;
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sd_login_monitor_get_timeout(m, &t);
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if (t == (uint64_t) -1)
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msec = -1;
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else {
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struct timespec ts;
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uint64_t n;
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clock_getttime(CLOCK_MONOTONIC, &ts);
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n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
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msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
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}</programlisting>
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<para>The code above does not do any error checking
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for brevity's sake. The calculated <literal>msec</literal>
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integer can be passed directly as
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<function>poll()</function>'s timeout
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parameter.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success
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<function>sd_login_monitor_new()</function>,
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<function>sd_login_monitor_flush()</function> and
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<function>sd_login_monitor_get_timeout()</function>
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return 0 or a positive integer. On success
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<function>sd_login_monitor_get_fd()</function> returns
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a Unix file descriptor. On success
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<function>sd_login_monitor_get_events()</function>
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returns a combination of <literal>POLLIN</literal>,
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<literal>POLLOUT</literal> and suchlike. On failure,
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these calls return a negative errno-style error
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code.</para>
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<para><function>sd_login_monitor_unref()</function>
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always returns NULL.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>The <function>sd_login_monitor_new()</function>,
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<function>sd_login_monitor_unref()</function>,
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<function>sd_login_monitor_flush()</function>,
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<function>sd_login_monitor_get_fd()</function>,
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<function>sd_login_monitor_get_events()</function> and
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<function>sd_login_monitor_get_timeout()</function>
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interfaces are available as shared library, which can
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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-login</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>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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