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514094f9 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
db9ecf05 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
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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> | |
e67d738a | 20 | <refname>sd_event_add_inotify_fd</refname> |
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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 <systemd/sd-event.h></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 | ||
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50 | <funcprototype> |
51 | <funcdef>int <function>sd_event_add_inotify_fd</function></funcdef> | |
52 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
53 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
54 | <paramdef>int <parameter>fd</parameter></paramdef> | |
55 | <paramdef>uint32_t <parameter>mask</parameter></paramdef> | |
56 | <paramdef>sd_event_inotify_handler_t <parameter>handler</parameter></paramdef> | |
57 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
58 | </funcprototype> | |
59 | ||
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60 | <funcprototype> |
61 | <funcdef>int <function>sd_event_source_get_inotify_mask</function></funcdef> | |
62 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
63 | <paramdef>uint32_t *<parameter>mask</parameter></paramdef> | |
64 | </funcprototype> | |
65 | ||
66 | </funcsynopsis> | |
67 | </refsynopsisdiv> | |
68 | ||
69 | <refsect1> | |
70 | <title>Description</title> | |
71 | ||
72 | <para><function>sd_event_add_inotify()</function> adds a new <citerefentry | |
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73 | project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> file |
74 | system inode event source to an event loop. The event loop object is specified in the | |
75 | <parameter>event</parameter> parameter, the event source object is returned in the | |
76 | <parameter>source</parameter> parameter. The <parameter>path</parameter> parameter specifies the path of | |
77 | the file system inode to watch. The <parameter>mask</parameter> parameter specifies which types of inode | |
78 | events to watch specifically. It must contain an OR-ed combination of <constant>IN_ACCESS</constant>, | |
79 | <constant>IN_ATTRIB</constant>, <constant>IN_CLOSE_WRITE</constant>, … flags. See <citerefentry | |
80 | project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> for | |
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81 | further information.</para> |
82 | ||
9809a788 | 83 | <para>The <parameter>handler</parameter> must reference a function to call when the inode changes or |
7611946e | 84 | <constant>NULL</constant>. The handler function will be passed the <parameter>userdata</parameter> pointer, |
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85 | which may be chosen freely by the caller. The handler also receives a pointer to a <structname>struct |
86 | inotify_event</structname> structure containing information about the inode event. The handler may return | |
87 | negative to signal an error (see below), other return values are ignored. If | |
88 | <parameter>handler</parameter> is <constant>NULL</constant>, a default handler that calls | |
89 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry> will be | |
90 | used.</para> | |
91 | ||
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92 | <para><function>sd_event_add_inotify_fd()</function> is identical to |
93 | <function>sd_event_add_inotify()</function>, except that it takes a file descriptor to an inode (possibly | |
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94 | an <constant>O_PATH</constant> one, but any other will do too) instead of a path in the file system. |
95 | </para> | |
e67d738a | 96 | |
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97 | <para>If multiple event sources are installed for the same inode the backing inotify watch descriptor is |
98 | automatically shared. The mask parameter may contain any flag defined by the inotify API, with the exception of | |
99 | <constant>IN_MASK_ADD</constant>.</para> | |
100 | ||
101 | <para>The handler is enabled continuously (<constant>SD_EVENT_ON</constant>), but this may be changed with | |
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102 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
103 | Alternatively, the <constant>IN_ONESHOT</constant> mask flag may be used to request | |
104 | <constant>SD_EVENT_ONESHOT</constant> mode. If the handler function returns a negative error code, it | |
105 | will be disabled after the invocation, even if the <constant>SD_EVENT_ON</constant> mode was requested | |
106 | before.</para> | |
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107 | |
108 | <para>As a special limitation the priority of inotify event sources may only be altered (see | |
109 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
110 | in the time between creation of the event source object with <function>sd_event_add_inotify()</function> and the | |
111 | beginning of the next event loop iteration. Attempts of changing the priority any later will be refused. Consider | |
112 | freeing and allocating a new inotify event source to change the priority at that point.</para> | |
113 | ||
114 | <para>To destroy an event source object use | |
115 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, but note | |
116 | that the event source is only removed from the event loop when all references to the event source are dropped. To | |
117 | make sure an event source does not fire anymore, even when there's still a reference to it kept, consider disabling | |
118 | it with | |
119 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
120 | ||
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121 | <para>If the second parameter of <function>sd_event_add_inotify()</function> is passed as |
122 | <constant>NULL</constant> no reference to the event source object is returned. In this case the event | |
123 | source is considered "floating", and will be destroyed implicitly when the event loop itself is | |
124 | destroyed.</para> | |
125 | ||
126 | <para>If the <parameter>handler</parameter> parameter to <function>sd_event_add_inotify()</function> is | |
127 | <constant>NULL</constant>, and the event source fires, this will be considered a request to exit the | |
128 | event loop. In this case, the <parameter>userdata</parameter> parameter, cast to an integer, is passed as | |
129 | the exit code parameter to | |
130 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
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131 | |
132 | <para><function>sd_event_source_get_inotify_mask()</function> retrieves the configured inotify watch mask of an | |
133 | event source created previously with <function>sd_event_add_inotify()</function>. It takes the event source object | |
134 | as the <parameter>source</parameter> parameter and a pointer to a <type>uint32_t</type> variable to return the mask | |
135 | in.</para> | |
136 | </refsect1> | |
137 | ||
138 | <refsect1> | |
139 | <title>Return Value</title> | |
140 | ||
141 | <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style | |
142 | error code.</para> | |
1eb54dc6 | 143 | |
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144 | <refsect2> |
145 | <title>Errors</title> | |
1eb54dc6 | 146 | |
b1de39de | 147 | <para>Returned errors may indicate the following problems:</para> |
1eb54dc6 | 148 | |
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149 | <variablelist> |
150 | <varlistentry> | |
151 | <term><constant>-ENOMEM</constant></term> | |
1eb54dc6 | 152 | |
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153 | <listitem><para>Not enough memory to allocate an object.</para></listitem> |
154 | </varlistentry> | |
1eb54dc6 | 155 | |
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156 | <varlistentry> |
157 | <term><constant>-EINVAL</constant></term> | |
1eb54dc6 | 158 | |
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159 | <listitem><para>An invalid argument has been passed. This includes specifying a mask with |
160 | <constant>IN_MASK_ADD</constant> set.</para></listitem> | |
161 | </varlistentry> | |
1eb54dc6 | 162 | |
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163 | <varlistentry> |
164 | <term><constant>-ESTALE</constant></term> | |
1eb54dc6 | 165 | |
b1de39de | 166 | <listitem><para>The event loop is already terminated.</para></listitem> |
1eb54dc6 | 167 | |
b1de39de | 168 | </varlistentry> |
1eb54dc6 | 169 | |
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170 | <varlistentry> |
171 | <term><constant>-ECHILD</constant></term> | |
1eb54dc6 | 172 | |
b1de39de | 173 | <listitem><para>The event loop has been created in a different process.</para></listitem> |
1eb54dc6 | 174 | |
b1de39de | 175 | </varlistentry> |
1eb54dc6 | 176 | |
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177 | <varlistentry> |
178 | <term><constant>-EDOM</constant></term> | |
1eb54dc6 | 179 | |
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180 | <listitem><para>The passed event source is not an inotify process event source.</para></listitem> |
181 | </varlistentry> | |
1eb54dc6 | 182 | |
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183 | <varlistentry> |
184 | <term><constant>-EBADF</constant></term> | |
185 | ||
186 | <listitem><para>The passed file descriptor is not valid.</para></listitem> | |
187 | </varlistentry> | |
188 | ||
189 | <varlistentry> | |
190 | <term><constant>-ENOSYS</constant></term> | |
191 | ||
192 | <listitem><para><function>sd_event_add_inotify_fd()</function> was called without | |
193 | <filename>/proc/</filename> mounted.</para></listitem> | |
194 | </varlistentry> | |
195 | ||
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196 | </variablelist> |
197 | </refsect2> | |
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198 | </refsect1> |
199 | ||
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200 | <refsect1> |
201 | <title>Examples</title> | |
202 | ||
203 | <example> | |
204 | <title>A simple program that uses inotify to monitor one or two directories</title> | |
205 | ||
206 | <programlisting><xi:include href="inotify-watch-tmp.c" parse="text" /></programlisting> | |
207 | </example> | |
208 | </refsect1> | |
209 | ||
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210 | <xi:include href="libsystemd-pkgconfig.xml" /> |
211 | ||
212 | <refsect1> | |
213 | <title>See Also</title> | |
214 | ||
215 | <para> | |
216 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
217 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
218 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
219 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
220 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
221 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
222 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
223 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
224 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
225 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
226 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
227 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
228 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
0bca2831 | 229 | <citerefentry><refentrytitle>sd_event_source_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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230 | <citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry> |
231 | </para> | |
232 | </refsect1> | |
233 | ||
234 | </refentry> |