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<refentry id="sd_login_monitor_new">

<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_flush</refname>

<refname>sd_login_monitor_get_fd</refname>

<refname>sd_login_monitor</refname>

<refpurpose>Monitor login sessions, seats and users</refpurpose>

</refnamediv>

<refsynopsisdiv>

<funcsynopsis>

<funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</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>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>

</funcsynopsis>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para><function>sd_login_monitor_new()</function> may

be used to monitor login session, users and seats. 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, or seat changes

state otherwise. The first parameter takes a string

which can be either <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) or <literal>uid</literal> (to get only

notifications when a user changes state in respect to

logins). If notifications shall be generated in all

these conditions, NULL may be passed. Note that in

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_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_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

POLLIN events. 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>

</refsect1>

<refsect1>

<title>Return Value</title>

<para>On success

<function>sd_login_monitor_new()</function> and

<function>sd_login_monitor_flush()</function> return 0

or a positive integer. On success

<function>sd_login_monitor_get_fd()</function> returns

a Unix file descriptor. On failure, these calls return

a negative errno-style error code.</para>

<para><function>sd_login_monitor_unref()</function>

always returns NULL.</para>

</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> and

<function>sd_login_monitor_get_fd()</function> interfaces

are available as shared library, which can be compiled

and linked to with the

<literal>libsystemd-login</literal>

<citerefentry><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>

</para>

</refsect1>

</refentry>