--- /dev/null
+<?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_monitor_new" conditional='HAVE_PAM'>
+
+ <refentryinfo>
+ <title>sd_login_monitor_new</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_monitor_new</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_login_monitor_new</refname>
+ <refname>sd_login_monitor_unref</refname>
+ <refname>sd_login_monitor_unrefp</refname>
+ <refname>sd_login_monitor_flush</refname>
+ <refname>sd_login_monitor_get_fd</refname>
+ <refname>sd_login_monitor_get_events</refname>
+ <refname>sd_login_monitor_get_timeout</refname>
+ <refname>sd_login_monitor</refname>
+ <refpurpose>Monitor login sessions, seats, users and virtual machines/containers</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-login.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_login_monitor_new</function></funcdef>
+ <paramdef>const char *<parameter>category</parameter></paramdef>
+ <paramdef>sd_login_monitor **<parameter>ret</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>sd_login_monitor *<function>sd_login_monitor_unref</function></funcdef>
+ <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>void <function>sd_login_monitor_unrefp</function></funcdef>
+ <paramdef>sd_login_monitor **<parameter>m</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_login_monitor_flush</function></funcdef>
+ <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_login_monitor_get_fd</function></funcdef>
+ <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_login_monitor_get_events</function></funcdef>
+ <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_login_monitor_get_timeout</function></funcdef>
+ <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef>
+ <paramdef>uint64_t *<parameter>timeout_usec</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_login_monitor_new()</function> may be used to
+ monitor login sessions, users, seats, and virtual
+ machines/containers. Via a monitor object a file descriptor can be
+ integrated into an application defined event loop which is woken
+ up each time a user logs in, logs out or a seat is added or
+ removed, or a session, user, seat or virtual machine/container
+ changes state otherwise. The first parameter takes a string which
+ can be <literal>seat</literal> (to get only notifications about
+ seats being added, removed or changed), <literal>session</literal>
+ (to get only notifications about sessions being created or removed
+ or changed), <literal>uid</literal> (to get only notifications
+ when a user changes state in respect to logins) or
+ <literal>machine</literal> (to get only notifications when a
+ virtual machine or container is started or stopped). If
+ notifications shall be generated in all these conditions,
+ <constant>NULL</constant> may be passed. Note that in the future
+ additional categories may be defined. The second parameter returns
+ a monitor object and needs to be freed with the
+ <function>sd_login_monitor_unref()</function> call after
+ use.</para>
+
+ <para><function>sd_login_monitor_unref()</function> may be used to
+ destroy a monitor object. Note that this will invalidate any file
+ descriptor returned by
+ <function>sd_login_monitor_get_fd()</function>.</para>
+
+ <para><function>sd_login_monitor_unrefp()</function> is similar to
+ <function>sd_login_monitor_unref()</function> but takes a pointer
+ to a pointer to an <type>sd_login_monitor</type> object. This call
+ is useful in conjunction with GCC's and LLVM's <ulink
+ url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
+ Variable Attribute</ulink>. Note that this function is defined as
+ inline function. Use a declaration like the following, in order to
+ allocate a login monitor object that is freed automatically as the
+ code block is left:</para>
+
+ <programlisting>{
+ __attribute__((cleanup(sd_login_monitor_unrefp)) sd_login_monitor *m = NULL;
+ int r;
+ …
+ r = sd_login_monitor_default(&m);
+ if (r < 0)
+ fprintf(stderr, "Failed to allocate login monitor object: %s\n", strerror(-r));
+ …
+}</programlisting>
+
+ <para><function>sd_login_monitor_flush()</function> may be used to
+ reset the wakeup state of the monitor object. Whenever an event
+ causes the monitor to wake up the event loop via the file
+ descriptor this function needs to be called to reset the wake-up
+ state. If this call is not invoked, the file descriptor will
+ immediately wake up the event loop again.</para>
+
+ <para><function>sd_login_monitor_unref()</function> and
+ <function>sd_login_monitor_unrefp()</function> execute no
+ operation if the passed in monitor object is
+ <constant>NULL</constant>.</para>
+
+ <para><function>sd_login_monitor_get_fd()</function> may be used
+ to retrieve the file descriptor of the monitor object that may be
+ integrated in an application defined event loop, based around
+ <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ or a similar interface. The application should include the
+ returned file descriptor as wake-up source for the events mask
+ returned by <function>sd_login_monitor_get_events()</function>. It
+ should pass a timeout value as returned by
+ <function>sd_login_monitor_get_timeout()</function>. Whenever a
+ wake-up is triggered the file descriptor needs to be reset via
+ <function>sd_login_monitor_flush()</function>. An application
+ needs to reread the login state with a function like
+ <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ or similar to determine what changed.</para>
+
+ <para><function>sd_login_monitor_get_events()</function> will
+ return the <function>poll()</function> mask to wait for. This
+ function will return a combination of <constant>POLLIN</constant>,
+ <constant>POLLOUT</constant> and similar to fill into the
+ <literal>.events</literal> field of <varname>struct
+ pollfd</varname>.</para>
+
+ <para><function>sd_login_monitor_get_timeout()</function> will
+ return a timeout value for usage in <function>poll()</function>.
+ This returns a value in microseconds since the epoch of
+ <constant>CLOCK_MONOTONIC</constant> for timing out
+ <function>poll()</function> in <varname>timeout_usec</varname>.
+ See
+ <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for details about <constant>CLOCK_MONOTONIC</constant>. If there
+ is no timeout to wait for this will fill in <constant>(uint64_t)
+ -1</constant> instead. Note that <function>poll()</function> takes
+ a relative timeout in milliseconds rather than an absolute timeout
+ in microseconds. To convert the absolute 'µs' timeout into
+ relative 'ms', use code like the following:</para>
+
+ <programlisting>uint64_t t;
+int msec;
+sd_login_monitor_get_timeout(m, &t);
+if (t == (uint64_t) -1)
+ msec = -1;
+else {
+ struct timespec ts;
+ uint64_t n;
+ clock_getttime(CLOCK_MONOTONIC, &ts);
+ n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
+ msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
+}</programlisting>
+
+ <para>The code above does not do any error checking for brevity's
+ sake. The calculated <varname>msec</varname> integer can be passed
+ directly as <function>poll()</function>'s timeout
+ parameter.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success,
+ <function>sd_login_monitor_new()</function>,
+ <function>sd_login_monitor_flush()</function> and
+ <function>sd_login_monitor_get_timeout()</function>
+ return 0 or a positive integer. On success,
+ <function>sd_login_monitor_get_fd()</function> returns
+ a Unix file descriptor. On success,
+ <function>sd_login_monitor_get_events()</function>
+ returns a combination of <constant>POLLIN</constant>,
+ <constant>POLLOUT</constant> and suchlike. On failure,
+ these calls return a negative errno-style error
+ code.</para>
+
+ <para><function>sd_login_monitor_unref()</function>
+ always returns <constant>NULL</constant>.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>An input parameter was invalid (out of range,
+ or NULL, where that is not accepted). The specified category to
+ watch is not known.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENOMEM</constant></term>
+
+ <listitem><para>Memory allocation failed.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>The <function>sd_login_monitor_new()</function>,
+ <function>sd_login_monitor_unref()</function>,
+ <function>sd_login_monitor_flush()</function>,
+ <function>sd_login_monitor_get_fd()</function>,
+ <function>sd_login_monitor_get_events()</function> and
+ <function>sd_login_monitor_get_timeout()</function>
+ interfaces are available as a shared library, which can be
+ compiled and linked to with the
+ <constant>libelogind</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ file.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>
~ianmdlvl / elogind.git / blobdiff