man/sd_login_monitor_new.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
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   8   Copyright 2010 Lennart Poettering
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  23
  24 <refentry id="sd_login_monitor_new">
  25
  26         <refentryinfo>
  27                 <title>sd_login_monitor_new</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>sd_login_monitor_new</refentrytitle>
  42                 <manvolnum>3</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>sd_login_monitor_new</refname>
  47                 <refname>sd_login_monitor_unref</refname>
  48                 <refname>sd_login_monitor_flush</refname>
  49                 <refname>sd_login_monitor_get_fd</refname>
  50                 <refpurpose>Monitor login sessions, seats and users</refpurpose>
  51         </refnamediv>
  52
  53         <refsynopsisdiv>
  54                 <funcsynopsis>
  55                         <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  56
  57                         <funcprototype>
  58                                 <funcdef>int <function>sd_login_monitor_new</function></funcdef>
  59                                 <paramdef>const char* <parameter>category</parameter></paramdef>
  60                                 <paramdef>sd_login_monitor** <parameter>ret</parameter></paramdef>
  61                         </funcprototype>
  62
  63                         <funcprototype>
  64                                 <funcdef>sd_login_monitor* <function>sd_login_monitor_unref</function></funcdef>
  65                                 <paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
  66                         </funcprototype>
  67
  68                         <funcprototype>
  69                                 <funcdef>int <function>sd_login_monitor_flush</function></funcdef>
  70                                 <paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
  71                         </funcprototype>
  72
  73                         <funcprototype>
  74                                 <funcdef>int <function>sd_login_monitor_get_fd</function></funcdef>
  75                                 <paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
  76                         </funcprototype>
  77
  78                 </funcsynopsis>
  79         </refsynopsisdiv>
  80
  81         <refsect1>
  82                 <title>Description</title>
  83
  84                 <para><function>sd_login_monitor_new()</function> may
  85                 be used to monitor login session, users and seats. Via
  86                 a monitor object a file descriptor can be integrated
  87                 into an application defined event loop which is woken
  88                 up each time a user logs in, logs out or a seat is
  89                 added or removed, or a session, user, or seat changes
  90                 state otherwise. The first parameter takes a string
  91                 which can be either <literal>seat</literal> (to get
  92                 only notifications about seats being added, removed or
  93                 changed), <literal>session</literal> (to get only
  94                 notifications about sessions being created or removed
  95                 or changed) or <literal>uid</literal> (to get only
  96                 notifications when a user changes state in respect to
  97                 logins). If notifications shall be generated in all
  98                 these conditions, NULL may be passed. Note that in
  99                 future additional categories may be defined. The
 100                 second parameter returns a monitor object and needs to
 101                 be freed with the
 102                 <function>sd_login_monitor_unref()</function> call
 103                 after use.</para>
 104
 105                 <para><function>sd_login_monitor_unref()</function>
 106                 may be used to destroy a monitor object. Note that
 107                 this will invalidate any file descriptor returned by
 108                 <function>sd_login_monitor_get_fd()</function>.</para>
 109
 110                 <para><function>sd_login_monitor_flush()</function>
 111                 may be used to reset the wakeup state of the monitor
 112                 object. Whenever an event causes the monitor to wake
 113                 up the event loop via the file descriptor this
 114                 function needs to be called to reset the wake-up
 115                 state. If this call is not invoked the file descriptor
 116                 will immediately wake up the event loop again.</para>
 117
 118                 <para><function>sd_login_monitor_get_fd()</function>
 119                 may be used to retrieve the file descriptor of the
 120                 monitor object that may be integrated in an
 121                 application defined event loop, based around
 122                 <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 123                 or a similar interface. The application should include
 124                 the returned file descriptor as wake up source for
 125                 POLLIN events. Whenever a wake-up is triggered the
 126                 file descriptor needs to be reset via
 127                 <function>sd_login_monitor_flush()</function>. An
 128                 application needs to reread the login state with a
 129                 function like
 130                 <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 131                 or similar to determine what changed.</para>
 132         </refsect1>
 133
 134         <refsect1>
 135                 <title>Return Value</title>
 136
 137                 <para>On success
 138                 <function>sd_login_monitor_new()</function> and
 139                 <function>sd_login_monitor_flush()</function> return 0
 140                 or a positive integer. On success
 141                 <function>sd_login_monitor_get_fd()</function> returns
 142                 a Unix file descriptor. On failure, these calls return
 143                 a negative errno-style error code.</para>
 144
 145                 <para><function>sd_login_monitor_unref()</function>
 146                 always returns NULL.</para>
 147         </refsect1>
 148
 149         <refsect1>
 150                 <title>Notes</title>
 151
 152                 <para>The <function>sd_login_monitor_new()</function>,
 153                 <function>sd_login_monitor_unref()</function>, <function>sd_login_monitor_flush()</function> and
 154                 <function>sd_login_monitor_get_fd()</function> interfaces
 155                 are available as shared library, which can be compiled
 156                 and linked to with the
 157                 <literal>libsystemd-login</literal>
 158                 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 159                 file.</para>
 160         </refsect1>
 161
 162         <refsect1>
 163                 <title>See Also</title>
 164
 165                 <para>
 166                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 167                         <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 168                         <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 169                 </para>
 170         </refsect1>
 171
 172 </refentry>