1
<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_login_monitor_new</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
11
background-color: #c60f0f;
15
h1:hover > a.headerlink, h2:hover > a.headerlink, h3:hover > a.headerlink, dt:hover > a.headerlink {
18
</style><a href="index.html">Index </a>·
19
<a href="systemd.directives.html">Directives </a>·
20
<a href="../python-systemd/index.html">Python </a>·
21
<a href="../libudev/index.html">libudev </a>·
22
<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 204</span><hr><div class="refentry"><a name="sd_login_monitor_new"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_login_monitor_new, sd_login_monitor_unref, sd_login_monitor_flush, sd_login_monitor_get_fd, sd_login_monitor_get_events, sd_login_monitor_get_timeout, sd_login_monitor — Monitor login sessions, seats, users and virtual machines/containers</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-login.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_login_monitor_new</b>(</code></td><td>const char* <var class="pdparam">category</var>, </td></tr><tr><td> </td><td>sd_login_monitor** <var class="pdparam">ret</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">sd_login_monitor* <b class="fsfunc">sd_login_monitor_unref</b>(</code></td><td>sd_login_monitor* <var class="pdparam">m</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_login_monitor_flush</b>(</code></td><td>sd_login_monitor* <var class="pdparam">m</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_login_monitor_get_fd</b>(</code></td><td>sd_login_monitor* <var class="pdparam">m</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_login_monitor_get_events</b>(</code></td><td>sd_login_monitor* <var class="pdparam">m</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_login_monitor_get_timeout</b>(</code></td><td>sd_login_monitor* <var class="pdparam">m</var>, </td></tr><tr><td> </td><td>uint64_t* <var class="pdparam">timeout_usec</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm259778088720"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_login_monitor_new()</code> may
23
be used to monitor login sessions, users, seats and
24
virtual machines/containers. Via a monitor object a
25
file descriptor can be integrated into an application
26
defined event loop which is woken up each time a user
27
logs in, logs out or a seat is added or removed, or a
28
session, user, seat or virtual machine/container
29
changes state otherwise. The first parameter takes a
30
string which can be <code class="literal">seat</code> (to get
31
only notifications about seats being added, removed or
32
changed), <code class="literal">session</code> (to get only
33
notifications about sessions being created or removed
34
or changed), <code class="literal">uid</code> (to get only
35
notifications when a user changes state in respect to
36
logins) or <code class="literal">machine</code> (to get only
37
notifications when a virtual machine or container is
38
started or stopped). If notifications shall be
39
generated in all these conditions, NULL may be
40
passed. Note that in the future additional categories
41
may be defined. The second parameter returns a monitor
42
object and needs to be freed with the
43
<code class="function">sd_login_monitor_unref()</code> call
44
after use.</p><p><code class="function">sd_login_monitor_unref()</code>
45
may be used to destroy a monitor object. Note that
46
this will invalidate any file descriptor returned by
47
<code class="function">sd_login_monitor_get_fd()</code>.</p><p><code class="function">sd_login_monitor_flush()</code>
48
may be used to reset the wakeup state of the monitor
49
object. Whenever an event causes the monitor to wake
50
up the event loop via the file descriptor this
51
function needs to be called to reset the wake-up
52
state. If this call is not invoked the file descriptor
53
will immediately wake up the event loop again.</p><p><code class="function">sd_login_monitor_get_fd()</code>
54
may be used to retrieve the file descriptor of the
55
monitor object that may be integrated in an
56
application defined event loop, based around
57
<a href="poll.html"><span class="citerefentry"><span class="refentrytitle">poll</span>(2)</span></a>
58
or a similar interface. The application should include
59
the returned file descriptor as wake-up source for the
60
events mask returned by
61
<code class="function">sd_login_monitor_get_events()</code>. It
62
should pass a timeout value as returned by
63
<code class="function">sd_login_monitor_get_timeout()</code>. Whenever
64
a wake-up is triggered the file descriptor needs to be
66
<code class="function">sd_login_monitor_flush()</code>. An
67
application needs to reread the login state with a
69
<a href="sd_get_seats.html"><span class="citerefentry"><span class="refentrytitle">sd_get_seats</span>(3)</span></a>
70
or similar to determine what changed.</p><p><code class="function">sd_login_monitor_get_events()</code>
71
will return the <code class="function">poll()</code> mask to
72
wait for. This function will return a combination of
73
<code class="literal">POLLIN</code>, <code class="literal">POLLOUT</code>
74
and similar to fill into the
75
<code class="literal">.events</code> field of <code class="literal">struct
76
pollfd</code>.</p><p><code class="function">sd_login_monitor_get_timeout()</code>
77
will return a timeout value for usage in
78
<code class="function">poll()</code>. This returns a value in
79
microseconds since the epoch of CLOCK_MONOTONIC for
80
timing out <code class="function">poll()</code> in
81
<code class="literal">timeout_usec</code>. See
82
<a href="clock_gettime.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a>
84
<code class="literal">CLOCK_MONOTONIC</code>. If there's no
85
timeout to wait for this will fill in
86
<code class="literal">(uint64_t) -1</code> instead. Note that
87
<code class="function">poll()</code> takes a relative timeout
88
in milliseconds rather than an absolute timeout in
89
microseconds. To convert the absolute 'us' timeout into
90
relative 'ms', use code like the following:</p><pre class="programlisting">uint64_t t;
92
sd_login_monitor_get_timeout(m, &t);
93
if (t == (uint64_t) -1)
98
clock_getttime(CLOCK_MONOTONIC, &ts);
99
n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
100
msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
101
}</pre><p>The code above does not do any error checking
102
for brevity's sake. The calculated <code class="literal">msec</code>
103
integer can be passed directly as
104
<code class="function">poll()</code>'s timeout
105
parameter.</p></div><div class="refsect1"><a name="idm259781952240"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success
106
<code class="function">sd_login_monitor_new()</code>,
107
<code class="function">sd_login_monitor_flush()</code> and
108
<code class="function">sd_login_monitor_get_timeout()</code>
109
return 0 or a positive integer. On success
110
<code class="function">sd_login_monitor_get_fd()</code> returns
111
a Unix file descriptor. On success
112
<code class="function">sd_login_monitor_get_events()</code>
113
returns a combination of <code class="literal">POLLIN</code>,
114
<code class="literal">POLLOUT</code> and suchlike. On failure,
115
these calls return a negative errno-style error
116
code.</p><p><code class="function">sd_login_monitor_unref()</code>
117
always returns NULL.</p></div><div class="refsect1"><a name="idm259781944896"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The <code class="function">sd_login_monitor_new()</code>,
118
<code class="function">sd_login_monitor_unref()</code>,
119
<code class="function">sd_login_monitor_flush()</code>,
120
<code class="function">sd_login_monitor_get_fd()</code>,
121
<code class="function">sd_login_monitor_get_events()</code> and
122
<code class="function">sd_login_monitor_get_timeout()</code>
123
interfaces are available as shared library, which can
124
be compiled and linked to with the
125
<code class="literal">libsystemd-login</code>
126
<a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
127
file.</p></div><div class="refsect1"><a name="idm259781937632"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
128
<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
129
<a href="sd-login.html"><span class="citerefentry"><span class="refentrytitle">sd-login</span>(3)</span></a>,
130
<a href="sd_get_seats.html"><span class="citerefentry"><span class="refentrytitle">sd_get_seats</span>(3)</span></a>,
131
<a href="poll.html"><span class="citerefentry"><span class="refentrytitle">poll</span>(2)</span></a>,
132
<a href="clock_gettime.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a>
133
</p></div></div></body></html>