man/sd_event_add_inotify.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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   5 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   6
   7 <refentry id="sd_event_add_inotify" xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_event_add_inotify</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_event_add_inotify</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_event_add_inotify</refname>
  21     <refname>sd_event_source_get_inotify_mask</refname>
  22     <refname>sd_event_inotify_handler_t</refname>
  23
  24     <refpurpose>Add an "inotify" file system inode event source to an event loop</refpurpose>
  25   </refnamediv>
  26
  27   <refsynopsisdiv>
  28     <funcsynopsis>
  29       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  30
  31       <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
  32
  33       <funcprototype>
  34         <funcdef>typedef int (*<function>sd_event_inotify_handler_t</function>)</funcdef>
  35         <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
  36         <paramdef>const struct inotify_event *<parameter>event</parameter></paramdef>
  37         <paramdef>void *<parameter>userdata</parameter></paramdef>
  38       </funcprototype>
  39
  40       <funcprototype>
  41         <funcdef>int <function>sd_event_add_inotify</function></funcdef>
  42         <paramdef>sd_event *<parameter>event</parameter></paramdef>
  43         <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
  44         <paramdef>const char *<parameter>path</parameter></paramdef>
  45         <paramdef>uint32_t <parameter>mask</parameter></paramdef>
  46         <paramdef>sd_event_inotify_handler_t <parameter>handler</parameter></paramdef>
  47         <paramdef>void *<parameter>userdata</parameter></paramdef>
  48       </funcprototype>
  49
  50       <funcprototype>
  51         <funcdef>int <function>sd_event_source_get_inotify_mask</function></funcdef>
  52         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  53         <paramdef>uint32_t *<parameter>mask</parameter></paramdef>
  54       </funcprototype>
  55
  56     </funcsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para><function>sd_event_add_inotify()</function> adds a new <citerefentry
  63     project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> file system inode
  64     event source to an event loop. The event loop object is specified in the <parameter>event</parameter> parameter,
  65     the event source object is returned in the <parameter>source</parameter> parameter. The <parameter>path</parameter>
  66     parameter specifies the path of the file system inode to watch. The <parameter>handler</parameter> must reference a
  67     function to call when the inode changes. The handler function will be passed the <parameter>userdata</parameter>
  68     pointer, which may be chosen freely by the caller. The handler also receives a pointer to a <structname>struct
  69     inotify_event</structname> structure containing information about the inode event. The <parameter>mask</parameter>
  70     parameter specifie which types of inode events to watch specifically. It must contain an OR-ed combination of
  71     <constant>IN_ACCESS</constant>, <constant>IN_ATTRIB</constant>, <constant>IN_CLOSE_WRITE</constant>, … flags. See
  72     <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
  73     further information.</para>
  74
  75     <para>If multiple event sources are installed for the same inode the backing inotify watch descriptor is
  76     automatically shared. The mask parameter may contain any flag defined by the inotify API, with the exception of
  77     <constant>IN_MASK_ADD</constant>.</para>
  78
  79     <para>The handler is enabled continuously (<constant>SD_EVENT_ON</constant>), but this may be changed with
  80     <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Alternatively,
  81     the <constant>IN_ONESHOT</constant> mask flag may be used to request <constant>SD_EVENT_ONESHOT</constant> mode.
  82     If the handler function returns a negative error code, it will be disabled after the invocation, even if the
  83     <constant>SD_EVENT_ON</constant> mode was requested before.
  84     </para>
  85
  86     <para>As a special limitation the priority of inotify event sources may only be altered (see
  87     <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
  88     in the time between creation of the event source object with <function>sd_event_add_inotify()</function> and the
  89     beginning of the next event loop iteration. Attempts of changing the priority any later will be refused. Consider
  90     freeing and allocating a new inotify event source to change the priority at that point.</para>
  91
  92     <para>To destroy an event source object use
  93     <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, but note
  94     that the event source is only removed from the event loop when all references to the event source are dropped. To
  95     make sure an event source does not fire anymore, even when there's still a reference to it kept, consider disabling
  96     it with
  97     <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  98
  99     <para>If the second parameter of <function>sd_event_add_inotify()</function> is passed as NULL no reference to the
 100     event source object is returned. In this case the event source is considered "floating", and will be destroyed
 101     implicitly when the event loop itself is destroyed.</para>
 102
 103     <para><function>sd_event_source_get_inotify_mask()</function> retrieves the configured inotify watch mask of an
 104     event source created previously with <function>sd_event_add_inotify()</function>. It takes the event source object
 105     as the <parameter>source</parameter> parameter and a pointer to a <type>uint32_t</type> variable to return the mask
 106     in.</para>
 107   </refsect1>
 108
 109   <refsect1>
 110     <title>Return Value</title>
 111
 112     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
 113     error code.</para>
 114   </refsect1>
 115
 116   <refsect1>
 117     <title>Errors</title>
 118
 119     <para>Returned errors may indicate the following problems:</para>
 120
 121     <variablelist>
 122       <varlistentry>
 123         <term><constant>-ENOMEM</constant></term>
 124
 125         <listitem><para>Not enough memory to allocate an object.</para></listitem>
 126       </varlistentry>
 127
 128       <varlistentry>
 129         <term><constant>-EINVAL</constant></term>
 130
 131         <listitem><para>An invalid argument has been passed. This includes specifying a mask with
 132         <constant>IN_MASK_ADD</constant> set.</para></listitem>
 133       </varlistentry>
 134
 135       <varlistentry>
 136         <term><constant>-ESTALE</constant></term>
 137
 138         <listitem><para>The event loop is already terminated.</para></listitem>
 139
 140       </varlistentry>
 141
 142       <varlistentry>
 143         <term><constant>-ECHILD</constant></term>
 144
 145         <listitem><para>The event loop has been created in a different process.</para></listitem>
 146
 147       </varlistentry>
 148
 149       <varlistentry>
 150         <term><constant>-EDOM</constant></term>
 151
 152         <listitem><para>The passed event source is not an inotify process event source.</para></listitem>
 153       </varlistentry>
 154
 155     </variablelist>
 156   </refsect1>
 157
 158   <refsect1>
 159     <title>Examples</title>
 160
 161     <example>
 162       <title>A simple program that uses inotify to monitor one or two directories</title>
 163
 164       <programlisting><xi:include href="inotify-watch-tmp.c" parse="text" /></programlisting>
 165     </example>
 166   </refsect1>
 167
 168   <xi:include href="libsystemd-pkgconfig.xml" />
 169
 170   <refsect1>
 171     <title>See Also</title>
 172
 173     <para>
 174       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 175       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 176       <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 177       <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 178       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 179       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 180       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 181       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 182       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 183       <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 184       <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 185       <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 186       <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 187       <citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 188     </para>
 189   </refsect1>
 190
 191 </refentry>