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514094f9 | 1 | <?xml version='1.0'?> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
eea10b26 | 3 | "http://www.oasis-open.org/docbook/xml/4.5/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> |
1eb54dc6 | 21 | <refname>sd_event_source_get_inotify_mask</refname> |
74c4231c | 22 | <refname>sd_event_source_get_inotify_path</refname> |
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23 | <refname>sd_event_inotify_handler_t</refname> |
24 | ||
25 | <refpurpose>Add an "inotify" file system inode event source to an event loop</refpurpose> | |
26 | </refnamediv> | |
27 | ||
28 | <refsynopsisdiv> | |
29 | <funcsynopsis> | |
30 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
31 | ||
32 | <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> | |
33 | ||
34 | <funcprototype> | |
35 | <funcdef>typedef int (*<function>sd_event_inotify_handler_t</function>)</funcdef> | |
36 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
37 | <paramdef>const struct inotify_event *<parameter>event</parameter></paramdef> | |
38 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
39 | </funcprototype> | |
40 | ||
41 | <funcprototype> | |
42 | <funcdef>int <function>sd_event_add_inotify</function></funcdef> | |
43 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
44 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
45 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
46 | <paramdef>uint32_t <parameter>mask</parameter></paramdef> | |
47 | <paramdef>sd_event_inotify_handler_t <parameter>handler</parameter></paramdef> | |
48 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
49 | </funcprototype> | |
50 | ||
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51 | <funcprototype> |
52 | <funcdef>int <function>sd_event_add_inotify_fd</function></funcdef> | |
53 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
54 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
55 | <paramdef>int <parameter>fd</parameter></paramdef> | |
56 | <paramdef>uint32_t <parameter>mask</parameter></paramdef> | |
57 | <paramdef>sd_event_inotify_handler_t <parameter>handler</parameter></paramdef> | |
58 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
59 | </funcprototype> | |
60 | ||
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61 | <funcprototype> |
62 | <funcdef>int <function>sd_event_source_get_inotify_mask</function></funcdef> | |
63 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
c1ab4458 | 64 | <paramdef>uint32_t *<parameter>ret</parameter></paramdef> |
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65 | </funcprototype> |
66 | ||
74c4231c YW |
67 | <funcprototype> |
68 | <funcdef>int <function>sd_event_source_get_inotify_path</function></funcdef> | |
69 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
70 | <paramdef>char **<parameter>ret</parameter></paramdef> | |
71 | </funcprototype> | |
72 | ||
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73 | </funcsynopsis> |
74 | </refsynopsisdiv> | |
75 | ||
76 | <refsect1> | |
77 | <title>Description</title> | |
78 | ||
79 | <para><function>sd_event_add_inotify()</function> adds a new <citerefentry | |
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80 | project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> file |
81 | system inode event source to an event loop. The event loop object is specified in the | |
82 | <parameter>event</parameter> parameter, the event source object is returned in the | |
83 | <parameter>source</parameter> parameter. The <parameter>path</parameter> parameter specifies the path of | |
84 | the file system inode to watch. The <parameter>mask</parameter> parameter specifies which types of inode | |
85 | events to watch specifically. It must contain an OR-ed combination of <constant>IN_ACCESS</constant>, | |
86 | <constant>IN_ATTRIB</constant>, <constant>IN_CLOSE_WRITE</constant>, … flags. See <citerefentry | |
87 | project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> for | |
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88 | further information.</para> |
89 | ||
9809a788 | 90 | <para>The <parameter>handler</parameter> must reference a function to call when the inode changes or |
7611946e | 91 | <constant>NULL</constant>. The handler function will be passed the <parameter>userdata</parameter> pointer, |
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92 | which may be chosen freely by the caller. The handler also receives a pointer to a <structname>struct |
93 | inotify_event</structname> structure containing information about the inode event. The handler may return | |
94 | negative to signal an error (see below), other return values are ignored. If | |
95 | <parameter>handler</parameter> is <constant>NULL</constant>, a default handler that calls | |
96 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry> will be | |
97 | used.</para> | |
98 | ||
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99 | <para><function>sd_event_add_inotify_fd()</function> is identical to |
100 | <function>sd_event_add_inotify()</function>, except that it takes a file descriptor to an inode (possibly | |
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101 | an <constant>O_PATH</constant> one, but any other will do too) instead of a path in the file system. |
102 | </para> | |
e67d738a | 103 | |
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104 | <para>If multiple event sources are installed for the same inode the backing inotify watch descriptor is |
105 | automatically shared. The mask parameter may contain any flag defined by the inotify API, with the exception of | |
106 | <constant>IN_MASK_ADD</constant>.</para> | |
107 | ||
108 | <para>The handler is enabled continuously (<constant>SD_EVENT_ON</constant>), but this may be changed with | |
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109 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
110 | Alternatively, the <constant>IN_ONESHOT</constant> mask flag may be used to request | |
111 | <constant>SD_EVENT_ONESHOT</constant> mode. If the handler function returns a negative error code, it | |
112 | will be disabled after the invocation, even if the <constant>SD_EVENT_ON</constant> mode was requested | |
113 | before.</para> | |
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114 | |
115 | <para>As a special limitation the priority of inotify event sources may only be altered (see | |
116 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
117 | in the time between creation of the event source object with <function>sd_event_add_inotify()</function> and the | |
118 | beginning of the next event loop iteration. Attempts of changing the priority any later will be refused. Consider | |
119 | freeing and allocating a new inotify event source to change the priority at that point.</para> | |
120 | ||
121 | <para>To destroy an event source object use | |
122 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, but note | |
123 | that the event source is only removed from the event loop when all references to the event source are dropped. To | |
124 | make sure an event source does not fire anymore, even when there's still a reference to it kept, consider disabling | |
125 | it with | |
126 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
127 | ||
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128 | <para>If the second parameter of <function>sd_event_add_inotify()</function> is passed as |
129 | <constant>NULL</constant> no reference to the event source object is returned. In this case the event | |
130 | source is considered "floating", and will be destroyed implicitly when the event loop itself is | |
131 | destroyed.</para> | |
132 | ||
133 | <para>If the <parameter>handler</parameter> parameter to <function>sd_event_add_inotify()</function> is | |
134 | <constant>NULL</constant>, and the event source fires, this will be considered a request to exit the | |
135 | event loop. In this case, the <parameter>userdata</parameter> parameter, cast to an integer, is passed as | |
136 | the exit code parameter to | |
137 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
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138 | |
139 | <para><function>sd_event_source_get_inotify_mask()</function> retrieves the configured inotify watch mask of an | |
140 | event source created previously with <function>sd_event_add_inotify()</function>. It takes the event source object | |
141 | as the <parameter>source</parameter> parameter and a pointer to a <type>uint32_t</type> variable to return the mask | |
142 | in.</para> | |
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143 | |
144 | <para><function>sd_event_source_get_inotify_path()</function> retrieves the target path of the configured | |
145 | inotify watch of an event source created previously with <function>sd_event_add_inotify()</function>. It | |
146 | takes the event source object as the <parameter>source</parameter> parameter and a pointer to a | |
147 | <type>char **</type> variable to return the path in. The caller needs to free the returned path.</para> | |
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148 | </refsect1> |
149 | ||
150 | <refsect1> | |
151 | <title>Return Value</title> | |
152 | ||
153 | <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style | |
154 | error code.</para> | |
1eb54dc6 | 155 | |
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156 | <refsect2> |
157 | <title>Errors</title> | |
1eb54dc6 | 158 | |
b1de39de | 159 | <para>Returned errors may indicate the following problems:</para> |
1eb54dc6 | 160 | |
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161 | <variablelist> |
162 | <varlistentry> | |
163 | <term><constant>-ENOMEM</constant></term> | |
1eb54dc6 | 164 | |
b1de39de ZJS |
165 | <listitem><para>Not enough memory to allocate an object.</para></listitem> |
166 | </varlistentry> | |
1eb54dc6 | 167 | |
b1de39de ZJS |
168 | <varlistentry> |
169 | <term><constant>-EINVAL</constant></term> | |
1eb54dc6 | 170 | |
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171 | <listitem><para>An invalid argument has been passed. This includes specifying a mask with |
172 | <constant>IN_MASK_ADD</constant> set.</para></listitem> | |
173 | </varlistentry> | |
1eb54dc6 | 174 | |
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175 | <varlistentry> |
176 | <term><constant>-ESTALE</constant></term> | |
1eb54dc6 | 177 | |
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178 | <listitem> |
179 | <para>Returned by <function>sd_event_source_add_inotify()</function> or | |
180 | <function>sd_event_source_add_inotify_fd()</function> when the event loop is already terminated. | |
181 | Returned by <function>sd_event_source_get_inotify_path()</function> when no active inode data is | |
182 | assigned to the event source, e.g. when the event source is disabled.</para> | |
183 | </listitem> | |
1eb54dc6 | 184 | |
b1de39de | 185 | </varlistentry> |
1eb54dc6 | 186 | |
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187 | <varlistentry> |
188 | <term><constant>-ECHILD</constant></term> | |
1eb54dc6 | 189 | |
2eeff0f4 | 190 | <listitem><para>The event loop has been created in a different process, library or module instance.</para></listitem> |
1eb54dc6 | 191 | |
b1de39de | 192 | </varlistentry> |
1eb54dc6 | 193 | |
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194 | <varlistentry> |
195 | <term><constant>-EDOM</constant></term> | |
1eb54dc6 | 196 | |
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197 | <listitem><para>The passed event source is not an inotify process event source.</para></listitem> |
198 | </varlistentry> | |
1eb54dc6 | 199 | |
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200 | <varlistentry> |
201 | <term><constant>-EBADF</constant></term> | |
202 | ||
fc6ec43c | 203 | <listitem><para>The passed file descriptor is not valid.</para></listitem> |
ec07c3c8 | 204 | |
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205 | </varlistentry> |
206 | ||
207 | <varlistentry> | |
208 | <term><constant>-ENOSYS</constant></term> | |
209 | ||
210 | <listitem><para><function>sd_event_add_inotify_fd()</function> was called without | |
fc6ec43c | 211 | <filename>/proc/</filename> mounted.</para></listitem> |
ec07c3c8 | 212 | |
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213 | </varlistentry> |
214 | ||
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215 | </variablelist> |
216 | </refsect2> | |
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217 | </refsect1> |
218 | ||
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219 | <refsect1> |
220 | <title>Examples</title> | |
221 | ||
222 | <example> | |
223 | <title>A simple program that uses inotify to monitor one or two directories</title> | |
224 | ||
225 | <programlisting><xi:include href="inotify-watch-tmp.c" parse="text" /></programlisting> | |
226 | </example> | |
227 | </refsect1> | |
228 | ||
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229 | <xi:include href="libsystemd-pkgconfig.xml" /> |
230 | ||
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231 | <refsect1> |
232 | <title>History</title> | |
00f95506 AK |
233 | <para><function>sd_event_inotify_handler_t()</function>, |
234 | <function>sd_event_add_inotify()</function>, and | |
235 | <function>sd_event_source_get_inotify_mask()</function> were added in version 239.</para> | |
69106f47 | 236 | <para><function>sd_event_add_inotify_fd()</function> was added in version 250.</para> |
74c4231c | 237 | <para><function>sd_event_source_get_inotify_path()</function> was added in version 256.</para> |
69106f47 AK |
238 | </refsect1> |
239 | ||
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240 | <refsect1> |
241 | <title>See Also</title> | |
242 | ||
13a69c12 DT |
243 | <para><simplelist type="inline"> |
244 | <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> | |
245 | <member><citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
246 | <member><citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
247 | <member><citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
248 | <member><citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
249 | <member><citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
250 | <member><citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
251 | <member><citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
252 | <member><citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
253 | <member><citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
254 | <member><citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
255 | <member><citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
256 | <member><citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
257 | <member><citerefentry><refentrytitle>sd_event_source_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
258 | <member><citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry></member> | |
259 | </simplelist></para> | |
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260 | </refsect1> |
261 | ||
262 | </refentry> |