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5aded36978
It is annoying when we have dead links on fd.o. Add project='man-pages|die-net|archlinux' to <citerefentry>-ies. In generated html, add external links to http://man7.org/linux/man-pages/man, http://linux.die.net/man/, https://www.archlinux.org/. By default, pages in sections 2 and 4 go to man7, since Michael Kerrisk is the autorative source on kernel related stuff. The rest of links goes to linux.die.net, because they have the manpages. Except for the pacman stuff, since it seems to be only available from archlinux.org. Poor gummiboot gets no link, because gummitboot(8) ain't to be found on the net. According to common wisdom, that would mean that it does not exist. But I have seen Kay using it, so I know it does, and deserves to be found. Can somebody be nice and put it up somewhere?
246 lines
12 KiB
XML
246 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, <constant>NULL</constant> 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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<constant>POLLIN</constant>, <constant>POLLOUT</constant>
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and similar to fill into the
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<literal>.events</literal> field of <varname>struct
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pollfd</varname>.</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 <constant>CLOCK_MONOTONIC</constant>
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for timing out <function>poll()</function> in
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<varname>timeout_usec</varname>. 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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<constant>CLOCK_MONOTONIC</constant>. If there is no
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timeout to wait for this will fill in
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<constant>(uint64_t) -1</constant> 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 <varname>msec</varname>
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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 <constant>POLLIN</constant>,
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<constant>POLLOUT</constant> 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 <constant>NULL</constant>.</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 a shared library, which can
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be compiled and linked to with the
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<constant>libsystemd</constant> <citerefentry project='die-net'><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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