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22 | <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 208</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="idm274676550160"></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 | |
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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 | |
| 14228c0d | 30 | string which can be "<code class="literal">seat</code>" (to get |
| 663996b3 | 31 | only notifications about seats being added, removed or |
| 14228c0d | 32 | changed), "<code class="literal">session</code>" (to get only |
| 663996b3 | 33 | notifications about sessions being created or removed |
| 14228c0d | 34 | or changed), "<code class="literal">uid</code>" (to get only |
| 663996b3 | 35 | notifications when a user changes state in respect to |
| 14228c0d | 36 | logins) or "<code class="literal">machine</code>" (to get only |
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37 | notifications when a virtual machine or container is |
| 38 | started or stopped). If notifications shall be | |
| 14228c0d | 39 | generated in all these conditions, <code class="constant">NULL</code> may be |
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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 | |
| 14228c0d | 52 | state. If this call is not invoked, the file descriptor |
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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 | |
| 65 | reset via | |
| 66 | <code class="function">sd_login_monitor_flush()</code>. An | |
| 67 | application needs to reread the login state with a | |
| 68 | function like | |
| 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 | |
| 14228c0d | 73 | <code class="constant">POLLIN</code>, <code class="constant">POLLOUT</code> |
| 663996b3 | 74 | and similar to fill into the |
| 14228c0d | 75 | "<code class="literal">.events</code>" field of <code class="varname">struct |
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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 | |
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79 | microseconds since the epoch of <code class="constant">CLOCK_MONOTONIC</code> |
| 80 | for timing out <code class="function">poll()</code> in | |
| 81 | <code class="varname">timeout_usec</code>. See | |
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82 | <a href="clock_gettime.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a> |
| 83 | for details about | |
| 14228c0d | 84 | <code class="constant">CLOCK_MONOTONIC</code>. If there is no |
| 663996b3 | 85 | timeout to wait for this will fill in |
| 14228c0d | 86 | <code class="constant">(uint64_t) -1</code> instead. Note that |
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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; | |
| 91 | int msec; | |
| 92 | sd_login_monitor_get_timeout(m, &t); | |
| 93 | if (t == (uint64_t) -1) | |
| 94 | msec = -1; | |
| 95 | else { | |
| 96 | struct timespec ts; | |
| 97 | uint64_t n; | |
| 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 | |
| 14228c0d | 102 | for brevity's sake. The calculated <code class="varname">msec</code> |
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103 | integer can be passed directly as |
| 104 | <code class="function">poll()</code>'s timeout | |
| 14228c0d | 105 | parameter.</p></div><div class="refsect1"><a name="idm274676514784"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success |
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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> | |
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113 | returns a combination of <code class="constant">POLLIN</code>, |
| 114 | <code class="constant">POLLOUT</code> and suchlike. On failure, | |
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115 | these calls return a negative errno-style error |
| 116 | code.</p><p><code class="function">sd_login_monitor_unref()</code> | |
| 14228c0d | 117 | always returns <code class="constant">NULL</code>.</p></div><div class="refsect1"><a name="idm274676507376"></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>, |
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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 | |
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125 | <code class="constant">libsystemd-login</code> <a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a> |
| 126 | file.</p></div><div class="refsect1"><a name="idm274671534880"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p> | |
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127 | <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>, |
| 128 | <a href="sd-login.html"><span class="citerefentry"><span class="refentrytitle">sd-login</span>(3)</span></a>, | |
| 129 | <a href="sd_get_seats.html"><span class="citerefentry"><span class="refentrytitle">sd_get_seats</span>(3)</span></a>, | |
| 130 | <a href="poll.html"><span class="citerefentry"><span class="refentrytitle">poll</span>(2)</span></a>, | |
| 131 | <a href="clock_gettime.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a> | |
| 132 | </p></div></div></body></html> |