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667c24a6a8
We don't need this right now, but we should keep our options open, in case we need more than just an fd for waking up.
244 lines
12 KiB
XML
244 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 and users</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 and seats. Via
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a monitor object a file descriptor can be integrated
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into an application defined event loop which is woken
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up each time a user logs in, logs out or a seat is
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added or removed, or a session, user, or seat changes
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state otherwise. The first parameter takes a string
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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) or <literal>uid</literal> (to get only
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notifications when a user changes state in respect to
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logins). If notifications shall be generated in all
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these conditions, NULL may be passed. Note that in the
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future additional categories may be defined. The
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second parameter returns a monitor object and needs to
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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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