man/sd_event_add_inotify.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_event_add_inotify" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>sd_event_add_inotify</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_event_add_inotify</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_event_add_inotify</refname>
  20     <refname>sd_event_source_get_inotify_mask</refname>
  21     <refname>sd_event_inotify_handler_t</refname>
  22
  23     <refpurpose>Add an "inotify" file system inode event source to an event loop</refpurpose>
  24   </refnamediv>
  25
  26   <refsynopsisdiv>
  27     <funcsynopsis>
  28       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  29
  30       <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
  31
  32       <funcprototype>
  33         <funcdef>typedef int (*<function>sd_event_inotify_handler_t</function>)</funcdef>
  34         <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
  35         <paramdef>const struct inotify_event *<parameter>event</parameter></paramdef>
  36         <paramdef>void *<parameter>userdata</parameter></paramdef>
  37       </funcprototype>
  38
  39       <funcprototype>
  40         <funcdef>int <function>sd_event_add_inotify</function></funcdef>
  41         <paramdef>sd_event *<parameter>event</parameter></paramdef>
  42         <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
  43         <paramdef>const char *<parameter>path</parameter></paramdef>
  44         <paramdef>uint32_t <parameter>mask</parameter></paramdef>
  45         <paramdef>sd_event_inotify_handler_t <parameter>handler</parameter></paramdef>
  46         <paramdef>void *<parameter>userdata</parameter></paramdef>
  47       </funcprototype>
  48
  49       <funcprototype>
  50         <funcdef>int <function>sd_event_source_get_inotify_mask</function></funcdef>
  51         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  52         <paramdef>uint32_t *<parameter>mask</parameter></paramdef>
  53       </funcprototype>
  54
  55     </funcsynopsis>
  56   </refsynopsisdiv>
  57
  58   <refsect1>
  59     <title>Description</title>
  60
  61     <para><function>sd_event_add_inotify()</function> adds a new <citerefentry
  62     project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> file system inode
  63     event source to an event loop. The event loop object is specified in the <parameter>event</parameter> parameter,
  64     the event source object is returned in the <parameter>source</parameter> parameter. The <parameter>path</parameter>
  65     parameter specifies the path of the file system inode to watch. The <parameter>handler</parameter> must reference a
  66     function to call when the inode changes. The handler function will be passed the <parameter>userdata</parameter>
  67     pointer, which may be chosen freely by the caller. The handler also receives a pointer to a <structname>struct
  68     inotify_event</structname> structure containing information about the inode event. The <parameter>mask</parameter>
  69     parameter specifie which types of inode events to watch specifically. It must contain an OR-ed combination of
  70     <constant>IN_ACCESS</constant>, <constant>IN_ATTRIB</constant>, <constant>IN_CLOSE_WRITE</constant>, … flags. See
  71     <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
  72     further information.</para>
  73
  74     <para>If multiple event sources are installed for the same inode the backing inotify watch descriptor is
  75     automatically shared. The mask parameter may contain any flag defined by the inotify API, with the exception of
  76     <constant>IN_MASK_ADD</constant>.</para>
  77
  78     <para>The handler is enabled continuously (<constant>SD_EVENT_ON</constant>), but this may be changed with
  79     <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Alternatively,
  80     the <constant>IN_ONESHOT</constant> mask flag may be used to request <constant>SD_EVENT_ONESHOT</constant> mode.
  81     If the handler function returns a negative error code, it will be disabled after the invocation, even if the
  82     <constant>SD_EVENT_ON</constant> mode was requested before.
  83     </para>
  84
  85     <para>As a special limitation the priority of inotify event sources may only be altered (see
  86     <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
  87     in the time between creation of the event source object with <function>sd_event_add_inotify()</function> and the
  88     beginning of the next event loop iteration. Attempts of changing the priority any later will be refused. Consider
  89     freeing and allocating a new inotify event source to change the priority at that point.</para>
  90
  91     <para>To destroy an event source object use
  92     <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, but note
  93     that the event source is only removed from the event loop when all references to the event source are dropped. To
  94     make sure an event source does not fire anymore, even when there's still a reference to it kept, consider disabling
  95     it with
  96     <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  97
  98     <para>If the second parameter of <function>sd_event_add_inotify()</function> is passed as NULL no reference to the
  99     event source object is returned. In this case the event source is considered "floating", and will be destroyed
 100     implicitly when the event loop itself is destroyed.</para>
 101
 102     <para><function>sd_event_source_get_inotify_mask()</function> retrieves the configured inotify watch mask of an
 103     event source created previously with <function>sd_event_add_inotify()</function>. It takes the event source object
 104     as the <parameter>source</parameter> parameter and a pointer to a <type>uint32_t</type> variable to return the mask
 105     in.</para>
 106   </refsect1>
 107
 108   <refsect1>
 109     <title>Return Value</title>
 110
 111     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
 112     error code.</para>
 113
 114     <refsect2>
 115       <title>Errors</title>
 116
 117       <para>Returned errors may indicate the following problems:</para>
 118
 119       <variablelist>
 120         <varlistentry>
 121           <term><constant>-ENOMEM</constant></term>
 122
 123           <listitem><para>Not enough memory to allocate an object.</para></listitem>
 124         </varlistentry>
 125
 126         <varlistentry>
 127           <term><constant>-EINVAL</constant></term>
 128
 129           <listitem><para>An invalid argument has been passed. This includes specifying a mask with
 130           <constant>IN_MASK_ADD</constant> set.</para></listitem>
 131         </varlistentry>
 132
 133         <varlistentry>
 134           <term><constant>-ESTALE</constant></term>
 135
 136           <listitem><para>The event loop is already terminated.</para></listitem>
 137
 138         </varlistentry>
 139
 140         <varlistentry>
 141           <term><constant>-ECHILD</constant></term>
 142
 143           <listitem><para>The event loop has been created in a different process.</para></listitem>
 144
 145         </varlistentry>
 146
 147         <varlistentry>
 148           <term><constant>-EDOM</constant></term>
 149
 150           <listitem><para>The passed event source is not an inotify process event source.</para></listitem>
 151         </varlistentry>
 152
 153       </variablelist>
 154     </refsect2>
 155   </refsect1>
 156
 157   <refsect1>
 158     <title>Examples</title>
 159
 160     <example>
 161       <title>A simple program that uses inotify to monitor one or two directories</title>
 162
 163       <programlisting><xi:include href="inotify-watch-tmp.c" parse="text" /></programlisting>
 164     </example>
 165   </refsect1>
 166
 167   <xi:include href="libsystemd-pkgconfig.xml" />
 168
 169   <refsect1>
 170     <title>See Also</title>
 171
 172     <para>
 173       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 174       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 175       <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 176       <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 177       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 178       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 179       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 180       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 181       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 182       <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 183       <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 184       <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 185       <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 186       <citerefentry><refentrytitle>sd_event_source_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 187       <citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 188     </para>
 189   </refsect1>
 190
 191 </refentry>