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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2010 Lennart Poettering | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
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11 | under the terms of the GNU Lesser General Public License as published by |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
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13 | (at your option) any later version. |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
5430f7f2 | 18 | Lesser General Public License for more details. |
0b3b020a | 19 | |
5430f7f2 | 20 | You should have received a copy of the GNU Lesser General Public License |
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21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. |
22 | --> | |
23 | ||
56ba3c78 | 24 | <refentry id="sd_login_monitor_new" conditional='HAVE_PAM'> |
0b3b020a | 25 | |
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26 | <refentryinfo> |
27 | <title>sd_login_monitor_new</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>Developer</contrib> | |
33 | <firstname>Lennart</firstname> | |
34 | <surname>Poettering</surname> | |
35 | <email>lennart@poettering.net</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>sd_login_monitor_new</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd_login_monitor_new</refname> | |
47 | <refname>sd_login_monitor_unref</refname> | |
4afd3348 | 48 | <refname>sd_login_monitor_unrefp</refname> |
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49 | <refname>sd_login_monitor_flush</refname> |
50 | <refname>sd_login_monitor_get_fd</refname> | |
51 | <refname>sd_login_monitor_get_events</refname> | |
52 | <refname>sd_login_monitor_get_timeout</refname> | |
53 | <refname>sd_login_monitor</refname> | |
54 | <refpurpose>Monitor login sessions, seats, users and virtual machines/containers</refpurpose> | |
55 | </refnamediv> | |
56 | ||
57 | <refsynopsisdiv> | |
58 | <funcsynopsis> | |
59 | <funcsynopsisinfo>#include <systemd/sd-login.h></funcsynopsisinfo> | |
60 | ||
61 | <funcprototype> | |
62 | <funcdef>int <function>sd_login_monitor_new</function></funcdef> | |
63 | <paramdef>const char *<parameter>category</parameter></paramdef> | |
64 | <paramdef>sd_login_monitor **<parameter>ret</parameter></paramdef> | |
65 | </funcprototype> | |
66 | ||
67 | <funcprototype> | |
68 | <funcdef>sd_login_monitor *<function>sd_login_monitor_unref</function></funcdef> | |
69 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
70 | </funcprototype> | |
71 | ||
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72 | <funcprototype> |
73 | <funcdef>void <function>sd_login_monitor_unrefp</function></funcdef> | |
74 | <paramdef>sd_login_monitor **<parameter>m</parameter></paramdef> | |
75 | </funcprototype> | |
76 | ||
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77 | <funcprototype> |
78 | <funcdef>int <function>sd_login_monitor_flush</function></funcdef> | |
79 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
80 | </funcprototype> | |
81 | ||
82 | <funcprototype> | |
83 | <funcdef>int <function>sd_login_monitor_get_fd</function></funcdef> | |
84 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
85 | </funcprototype> | |
86 | ||
87 | <funcprototype> | |
88 | <funcdef>int <function>sd_login_monitor_get_events</function></funcdef> | |
89 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
90 | </funcprototype> | |
91 | ||
92 | <funcprototype> | |
93 | <funcdef>int <function>sd_login_monitor_get_timeout</function></funcdef> | |
94 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
95 | <paramdef>uint64_t *<parameter>timeout_usec</parameter></paramdef> | |
96 | </funcprototype> | |
97 | ||
98 | </funcsynopsis> | |
99 | </refsynopsisdiv> | |
100 | ||
101 | <refsect1> | |
102 | <title>Description</title> | |
103 | ||
104 | <para><function>sd_login_monitor_new()</function> may be used to | |
105 | monitor login sessions, users, seats, and virtual | |
106 | machines/containers. Via a monitor object a file descriptor can be | |
107 | integrated into an application defined event loop which is woken | |
108 | up each time a user logs in, logs out or a seat is added or | |
109 | removed, or a session, user, seat or virtual machine/container | |
110 | changes state otherwise. The first parameter takes a string which | |
111 | can be <literal>seat</literal> (to get only notifications about | |
112 | seats being added, removed or changed), <literal>session</literal> | |
113 | (to get only notifications about sessions being created or removed | |
114 | or changed), <literal>uid</literal> (to get only notifications | |
115 | when a user changes state in respect to logins) or | |
116 | <literal>machine</literal> (to get only notifications when a | |
117 | virtual machine or container is started or stopped). If | |
118 | notifications shall be generated in all these conditions, | |
119 | <constant>NULL</constant> may be passed. Note that in the future | |
120 | additional categories may be defined. The second parameter returns | |
121 | a monitor object and needs to be freed with the | |
122 | <function>sd_login_monitor_unref()</function> call after | |
123 | use.</para> | |
124 | ||
125 | <para><function>sd_login_monitor_unref()</function> may be used to | |
126 | destroy a monitor object. Note that this will invalidate any file | |
127 | descriptor returned by | |
128 | <function>sd_login_monitor_get_fd()</function>.</para> | |
129 | ||
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130 | <para><function>sd_login_monitor_unrefp()</function> is similar to |
131 | <function>sd_login_monitor_unref()</function> but takes a pointer | |
132 | to a pointer to an <type>sd_login_monitor</type> object. This call | |
133 | is useful in conjunction with GCC's and LLVM's <ulink | |
134 | url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up | |
135 | Variable Attribute</ulink>. Note that this function is defined as | |
136 | inline function. Use a declaration like the following, in order to | |
137 | allocate a login monitor object that is freed automatically as the | |
138 | code block is left:</para> | |
139 | ||
140 | <programlisting>{ | |
141 | __attribute__((cleanup(sd_login_monitor_unrefp)) sd_login_monitor *m = NULL; | |
142 | int r; | |
143 | … | |
144 | r = sd_login_monitor_default(&m); | |
145 | if (r < 0) | |
146 | fprintf(stderr, "Failed to allocate login monitor object: %s\n", strerror(-r)); | |
147 | … | |
148 | }</programlisting> | |
149 | ||
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150 | <para><function>sd_login_monitor_flush()</function> may be used to |
151 | reset the wakeup state of the monitor object. Whenever an event | |
152 | causes the monitor to wake up the event loop via the file | |
153 | descriptor this function needs to be called to reset the wake-up | |
154 | state. If this call is not invoked, the file descriptor will | |
155 | immediately wake up the event loop again.</para> | |
156 | ||
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157 | <para><function>sd_login_monitor_unref()</function> and |
158 | <function>sd_login_monitor_unrefp()</function> execute no | |
159 | operation if the passed in monitor object is | |
160 | <constant>NULL</constant>.</para> | |
161 | ||
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162 | <para><function>sd_login_monitor_get_fd()</function> may be used |
163 | to retrieve the file descriptor of the monitor object that may be | |
164 | integrated in an application defined event loop, based around | |
165 | <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
166 | or a similar interface. The application should include the | |
167 | returned file descriptor as wake-up source for the events mask | |
168 | returned by <function>sd_login_monitor_get_events()</function>. It | |
169 | should pass a timeout value as returned by | |
170 | <function>sd_login_monitor_get_timeout()</function>. Whenever a | |
171 | wake-up is triggered the file descriptor needs to be reset via | |
172 | <function>sd_login_monitor_flush()</function>. An application | |
173 | needs to reread the login state with a function like | |
174 | <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
175 | or similar to determine what changed.</para> | |
176 | ||
177 | <para><function>sd_login_monitor_get_events()</function> will | |
178 | return the <function>poll()</function> mask to wait for. This | |
179 | function will return a combination of <constant>POLLIN</constant>, | |
180 | <constant>POLLOUT</constant> and similar to fill into the | |
181 | <literal>.events</literal> field of <varname>struct | |
182 | pollfd</varname>.</para> | |
183 | ||
184 | <para><function>sd_login_monitor_get_timeout()</function> will | |
185 | return a timeout value for usage in <function>poll()</function>. | |
186 | This returns a value in microseconds since the epoch of | |
187 | <constant>CLOCK_MONOTONIC</constant> for timing out | |
188 | <function>poll()</function> in <varname>timeout_usec</varname>. | |
189 | See | |
190 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
191 | for details about <constant>CLOCK_MONOTONIC</constant>. If there | |
192 | is no timeout to wait for this will fill in <constant>(uint64_t) | |
193 | -1</constant> instead. Note that <function>poll()</function> takes | |
194 | a relative timeout in milliseconds rather than an absolute timeout | |
707b66c6 | 195 | in microseconds. To convert the absolute 'µs' timeout into |
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196 | relative 'ms', use code like the following:</para> |
197 | ||
198 | <programlisting>uint64_t t; | |
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199 | int msec; |
200 | sd_login_monitor_get_timeout(m, &t); | |
201 | if (t == (uint64_t) -1) | |
707b66c6 | 202 | msec = -1; |
667c24a6 | 203 | else { |
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204 | struct timespec ts; |
205 | uint64_t n; | |
206 | clock_getttime(CLOCK_MONOTONIC, &ts); | |
207 | n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000; | |
208 | msec = t > n ? (int) ((t - n + 999) / 1000) : 0; | |
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209 | }</programlisting> |
210 | ||
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211 | <para>The code above does not do any error checking for brevity's |
212 | sake. The calculated <varname>msec</varname> integer can be passed | |
213 | directly as <function>poll()</function>'s timeout | |
214 | parameter.</para> | |
215 | </refsect1> | |
216 | ||
217 | <refsect1> | |
218 | <title>Return Value</title> | |
219 | ||
220 | <para>On success, | |
221 | <function>sd_login_monitor_new()</function>, | |
222 | <function>sd_login_monitor_flush()</function> and | |
223 | <function>sd_login_monitor_get_timeout()</function> | |
224 | return 0 or a positive integer. On success, | |
225 | <function>sd_login_monitor_get_fd()</function> returns | |
226 | a Unix file descriptor. On success, | |
227 | <function>sd_login_monitor_get_events()</function> | |
228 | returns a combination of <constant>POLLIN</constant>, | |
229 | <constant>POLLOUT</constant> and suchlike. On failure, | |
230 | these calls return a negative errno-style error | |
231 | code.</para> | |
232 | ||
233 | <para><function>sd_login_monitor_unref()</function> | |
234 | always returns <constant>NULL</constant>.</para> | |
235 | </refsect1> | |
236 | ||
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237 | <refsect1> |
238 | <title>Errors</title> | |
239 | ||
240 | <para>Returned errors may indicate the following problems:</para> | |
241 | ||
242 | <variablelist> | |
243 | ||
244 | <varlistentry> | |
245 | <term><constant>-EINVAL</constant></term> | |
246 | ||
247 | <listitem><para>An input parameter was invalid (out of range, | |
7ca41557 | 248 | or NULL, where that is not accepted). The specified category to |
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249 | watch is not known.</para></listitem> |
250 | </varlistentry> | |
251 | ||
252 | <varlistentry> | |
253 | <term><constant>-ENOMEM</constant></term> | |
254 | ||
255 | <listitem><para>Memory allocation failed.</para></listitem> | |
256 | </varlistentry> | |
257 | </variablelist> | |
258 | </refsect1> | |
259 | ||
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260 | <refsect1> |
261 | <title>Notes</title> | |
262 | ||
263 | <para>The <function>sd_login_monitor_new()</function>, | |
264 | <function>sd_login_monitor_unref()</function>, | |
265 | <function>sd_login_monitor_flush()</function>, | |
266 | <function>sd_login_monitor_get_fd()</function>, | |
267 | <function>sd_login_monitor_get_events()</function> and | |
268 | <function>sd_login_monitor_get_timeout()</function> | |
269 | interfaces are available as a shared library, which can be | |
270 | compiled and linked to with the | |
271 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
272 | file.</para> | |
273 | </refsect1> | |
274 | ||
275 | <refsect1> | |
276 | <title>See Also</title> | |
277 | ||
278 | <para> | |
279 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
280 | <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
281 | <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
282 | <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
283 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
284 | </para> | |
285 | </refsect1> | |
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286 | |
287 | </refentry> |