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systemd/docs/libudev/html/libudev-udev-monitor.html
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2014-07-11 02:23:25 +02:00

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<a href="#libudev-udev-monitor.synopsis" class="shortcut">Top</a>
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<a href="#libudev-udev-monitor.description" class="shortcut">Description</a>
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<div class="refentry">
<a name="libudev-udev-monitor"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="libudev-udev-monitor.top_of_page"></a>udev_monitor</span></h2>
<p>udev_monitor — device event source</p>
</td>
<td valign="top" align="right"></td>
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<div class="refsynopsisdiv">
<a name="libudev-udev-monitor.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">struct <a class="link" href="libudev-udev-monitor.html#udev-monitor" title="struct udev_monitor">udev_monitor</a>;
struct <a class="link" href="libudev-udev-monitor.html#udev-monitor" title="struct udev_monitor"><span class="returnvalue">udev_monitor</span></a> * <a class="link" href="libudev-udev-monitor.html#udev-monitor-ref" title="udev_monitor_ref ()">udev_monitor_ref</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);
struct <a class="link" href="libudev-udev-monitor.html#udev-monitor" title="struct udev_monitor"><span class="returnvalue">udev_monitor</span></a> * <a class="link" href="libudev-udev-monitor.html#udev-monitor-unref" title="udev_monitor_unref ()">udev_monitor_unref</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);
struct <a class="link" href="libudev-udev.html#udev" title="struct udev"><span class="returnvalue">udev</span></a> * <a class="link" href="libudev-udev-monitor.html#udev-monitor-get-udev" title="udev_monitor_get_udev ()">udev_monitor_get_udev</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);
struct <a class="link" href="libudev-udev-monitor.html#udev-monitor" title="struct udev_monitor"><span class="returnvalue">udev_monitor</span></a> * <a class="link" href="libudev-udev-monitor.html#udev-monitor-new-from-netlink" title="udev_monitor_new_from_netlink ()">udev_monitor_new_from_netlink</a> (<em class="parameter"><code><span class="type">struct udev</span> *udev</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *name</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libudev-udev-monitor.html#udev-monitor-enable-receiving" title="udev_monitor_enable_receiving ()">udev_monitor_enable_receiving</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libudev-udev-monitor.html#udev-monitor-set-receive-buffer-size" title="udev_monitor_set_receive_buffer_size ()">udev_monitor_set_receive_buffer_size</a>
(<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>,
<em class="parameter"><code><span class="type">int</span> size</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libudev-udev-monitor.html#udev-monitor-get-fd" title="udev_monitor_get_fd ()">udev_monitor_get_fd</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);
struct <a class="link" href="libudev-udev-device.html#udev-device" title="struct udev_device"><span class="returnvalue">udev_device</span></a> * <a class="link" href="libudev-udev-monitor.html#udev-monitor-receive-device" title="udev_monitor_receive_device ()">udev_monitor_receive_device</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libudev-udev-monitor.html#udev-monitor-filter-add-match-subsystem-devtype" title="udev_monitor_filter_add_match_subsystem_devtype ()">udev_monitor_filter_add_match_subsystem_devtype</a>
(<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *subsystem</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *devtype</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libudev-udev-monitor.html#udev-monitor-filter-add-match-tag" title="udev_monitor_filter_add_match_tag ()">udev_monitor_filter_add_match_tag</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *tag</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libudev-udev-monitor.html#udev-monitor-filter-update" title="udev_monitor_filter_update ()">udev_monitor_filter_update</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libudev-udev-monitor.html#udev-monitor-filter-remove" title="udev_monitor_filter_remove ()">udev_monitor_filter_remove</a> (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);
</pre>
</div>
<div class="refsect1">
<a name="libudev-udev-monitor.description"></a><h2>Description</h2>
<p>
Connects to a device event source.
</p>
</div>
<div class="refsect1">
<a name="libudev-udev-monitor.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="udev-monitor"></a><h3>struct udev_monitor</h3>
<pre class="programlisting">struct udev_monitor;</pre>
<p>
Opaque object handling an event source.
</p>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-ref"></a><h3>udev_monitor_ref ()</h3>
<pre class="programlisting">struct <a class="link" href="libudev-udev-monitor.html#udev-monitor" title="struct udev_monitor"><span class="returnvalue">udev_monitor</span></a> * udev_monitor_ref (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);</pre>
<p>
Take a reference of a udev monitor.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>udev monitor</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the passed udev monitor</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-unref"></a><h3>udev_monitor_unref ()</h3>
<pre class="programlisting">struct <a class="link" href="libudev-udev-monitor.html#udev-monitor" title="struct udev_monitor"><span class="returnvalue">udev_monitor</span></a> * udev_monitor_unref (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);</pre>
<p>
Drop a reference of a udev monitor. If the refcount reaches zero,
the bound socket will be closed, and the resources of the monitor
will be released.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>udev monitor</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td><span class="type">NULL</span></td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-get-udev"></a><h3>udev_monitor_get_udev ()</h3>
<pre class="programlisting">struct <a class="link" href="libudev-udev.html#udev" title="struct udev"><span class="returnvalue">udev</span></a> * udev_monitor_get_udev (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);</pre>
<p>
Retrieve the udev library context the monitor was created with.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>udev monitor</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the udev library context</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-new-from-netlink"></a><h3>udev_monitor_new_from_netlink ()</h3>
<pre class="programlisting">struct <a class="link" href="libudev-udev-monitor.html#udev-monitor" title="struct udev_monitor"><span class="returnvalue">udev_monitor</span></a> * udev_monitor_new_from_netlink (<em class="parameter"><code><span class="type">struct udev</span> *udev</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *name</code></em>);</pre>
<p>
Create new udev monitor and connect to a specified event
source. Valid sources identifiers are "udev" and "kernel".
</p>
<p>
Applications should usually not connect directly to the
"kernel" events, because the devices might not be useable
at that time, before udev has configured them, and created
device nodes. Accessing devices at the same time as udev,
might result in unpredictable behavior. The "udev" events
are sent out after udev has finished its event processing,
all rules have been processed, and needed device nodes are
created.
</p>
<p>
The initial refcount is 1, and needs to be decremented to
release the resources of the udev monitor.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev</code></em> :</span></p></td>
<td>udev library context</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>name</code></em> :</span></p></td>
<td>name of event source</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a new udev monitor, or <span class="type">NULL</span>, in case of an error</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-enable-receiving"></a><h3>udev_monitor_enable_receiving ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> udev_monitor_enable_receiving (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);</pre>
<p>
Binds the <em class="parameter"><code>udev_monitor</code></em> socket to the event source.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>the monitor which should receive events</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, otherwise a negative error value.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-set-receive-buffer-size"></a><h3>udev_monitor_set_receive_buffer_size ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> udev_monitor_set_receive_buffer_size
(<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>,
<em class="parameter"><code><span class="type">int</span> size</code></em>);</pre>
<p>
Set the size of the kernel socket buffer. This call needs the
appropriate privileges to succeed.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>the monitor which should receive events</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>size</code></em> :</span></p></td>
<td>the size in bytes</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, otherwise -1 on error.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-get-fd"></a><h3>udev_monitor_get_fd ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> udev_monitor_get_fd (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);</pre>
<p>
Retrieve the socket file descriptor associated with the monitor.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>udev monitor</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the socket file descriptor</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-receive-device"></a><h3>udev_monitor_receive_device ()</h3>
<pre class="programlisting">struct <a class="link" href="libudev-udev-device.html#udev-device" title="struct udev_device"><span class="returnvalue">udev_device</span></a> * udev_monitor_receive_device (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);</pre>
<p>
Receive data from the udev monitor socket, allocate a new udev
device, fill in the received data, and return the device.
</p>
<p>
Only socket connections with uid=0 are accepted.
</p>
<p>
The monitor socket is by default set to NONBLOCK. A variant of <code class="function">poll()</code> on
the file descriptor returned by <a class="link" href="libudev-udev-monitor.html#udev-monitor-get-fd" title="udev_monitor_get_fd ()"><code class="function">udev_monitor_get_fd()</code></a> should to be used to
wake up when new devices arrive, or alternatively the file descriptor
switched into blocking mode.
</p>
<p>
The initial refcount is 1, and needs to be decremented to
release the resources of the udev device.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>udev monitor</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a new udev device, or <span class="type">NULL</span>, in case of an error</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-filter-add-match-subsystem-devtype"></a><h3>udev_monitor_filter_add_match_subsystem_devtype ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> udev_monitor_filter_add_match_subsystem_devtype
(<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *subsystem</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *devtype</code></em>);</pre>
<p>
This filter is efficiently executed inside the kernel, and libudev subscribers
will usually not be woken up for devices which do not match.
</p>
<p>
The filter must be installed before the monitor is switched to listening mode.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>the monitor</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>subsystem</code></em> :</span></p></td>
<td>the subsystem value to match the incoming devices against</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>devtype</code></em> :</span></p></td>
<td>the devtype value to match the incoming devices against</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, otherwise a negative error value.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-filter-add-match-tag"></a><h3>udev_monitor_filter_add_match_tag ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> udev_monitor_filter_add_match_tag (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *tag</code></em>);</pre>
<p>
This filter is efficiently executed inside the kernel, and libudev subscribers
will usually not be woken up for devices which do not match.
</p>
<p>
The filter must be installed before the monitor is switched to listening mode.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>the monitor</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>tag</code></em> :</span></p></td>
<td>the name of a tag</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, otherwise a negative error value.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-filter-update"></a><h3>udev_monitor_filter_update ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> udev_monitor_filter_update (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);</pre>
<p>
Update the installed socket filter. This is only needed,
if the filter was removed or changed.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>monitor</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, otherwise a negative error value.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="udev-monitor-filter-remove"></a><h3>udev_monitor_filter_remove ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> udev_monitor_filter_remove (<em class="parameter"><code><span class="type">struct udev_monitor</span> *udev_monitor</code></em>);</pre>
<p>
Remove all filters from monitor.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>udev_monitor</code></em> :</span></p></td>
<td>monitor</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, otherwise a negative error value.</td>
</tr>
</tbody>
</table></div>
</div>
</div>
</div>
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