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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"> |
0b3b020a LP |
4 | |
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
7d6b2723 ZJS |
9 | <refentry id="sd_login_monitor_new" conditional='HAVE_PAM' |
10 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
0b3b020a | 11 | |
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12 | <refentryinfo> |
13 | <title>sd_login_monitor_new</title> | |
14 | <productname>systemd</productname> | |
15 | ||
16 | <authorgroup> | |
17 | <author> | |
18 | <contrib>Developer</contrib> | |
19 | <firstname>Lennart</firstname> | |
20 | <surname>Poettering</surname> | |
21 | <email>lennart@poettering.net</email> | |
22 | </author> | |
23 | </authorgroup> | |
24 | </refentryinfo> | |
25 | ||
26 | <refmeta> | |
27 | <refentrytitle>sd_login_monitor_new</refentrytitle> | |
28 | <manvolnum>3</manvolnum> | |
29 | </refmeta> | |
30 | ||
31 | <refnamediv> | |
32 | <refname>sd_login_monitor_new</refname> | |
33 | <refname>sd_login_monitor_unref</refname> | |
4afd3348 | 34 | <refname>sd_login_monitor_unrefp</refname> |
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35 | <refname>sd_login_monitor_flush</refname> |
36 | <refname>sd_login_monitor_get_fd</refname> | |
37 | <refname>sd_login_monitor_get_events</refname> | |
38 | <refname>sd_login_monitor_get_timeout</refname> | |
39 | <refname>sd_login_monitor</refname> | |
40 | <refpurpose>Monitor login sessions, seats, users and virtual machines/containers</refpurpose> | |
41 | </refnamediv> | |
42 | ||
43 | <refsynopsisdiv> | |
44 | <funcsynopsis> | |
45 | <funcsynopsisinfo>#include <systemd/sd-login.h></funcsynopsisinfo> | |
46 | ||
47 | <funcprototype> | |
48 | <funcdef>int <function>sd_login_monitor_new</function></funcdef> | |
49 | <paramdef>const char *<parameter>category</parameter></paramdef> | |
50 | <paramdef>sd_login_monitor **<parameter>ret</parameter></paramdef> | |
51 | </funcprototype> | |
52 | ||
53 | <funcprototype> | |
54 | <funcdef>sd_login_monitor *<function>sd_login_monitor_unref</function></funcdef> | |
55 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
56 | </funcprototype> | |
57 | ||
4afd3348 LP |
58 | <funcprototype> |
59 | <funcdef>void <function>sd_login_monitor_unrefp</function></funcdef> | |
60 | <paramdef>sd_login_monitor **<parameter>m</parameter></paramdef> | |
61 | </funcprototype> | |
62 | ||
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63 | <funcprototype> |
64 | <funcdef>int <function>sd_login_monitor_flush</function></funcdef> | |
65 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
66 | </funcprototype> | |
67 | ||
68 | <funcprototype> | |
69 | <funcdef>int <function>sd_login_monitor_get_fd</function></funcdef> | |
70 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
71 | </funcprototype> | |
72 | ||
73 | <funcprototype> | |
74 | <funcdef>int <function>sd_login_monitor_get_events</function></funcdef> | |
75 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
76 | </funcprototype> | |
77 | ||
78 | <funcprototype> | |
79 | <funcdef>int <function>sd_login_monitor_get_timeout</function></funcdef> | |
80 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
81 | <paramdef>uint64_t *<parameter>timeout_usec</parameter></paramdef> | |
82 | </funcprototype> | |
83 | ||
84 | </funcsynopsis> | |
85 | </refsynopsisdiv> | |
86 | ||
87 | <refsect1> | |
88 | <title>Description</title> | |
89 | ||
90 | <para><function>sd_login_monitor_new()</function> may be used to | |
91 | monitor login sessions, users, seats, and virtual | |
92 | machines/containers. Via a monitor object a file descriptor can be | |
93 | integrated into an application defined event loop which is woken | |
94 | up each time a user logs in, logs out or a seat is added or | |
95 | removed, or a session, user, seat or virtual machine/container | |
96 | changes state otherwise. The first parameter takes a string which | |
97 | can be <literal>seat</literal> (to get only notifications about | |
98 | seats being added, removed or changed), <literal>session</literal> | |
99 | (to get only notifications about sessions being created or removed | |
100 | or changed), <literal>uid</literal> (to get only notifications | |
101 | when a user changes state in respect to logins) or | |
102 | <literal>machine</literal> (to get only notifications when a | |
103 | virtual machine or container is started or stopped). If | |
104 | notifications shall be generated in all these conditions, | |
105 | <constant>NULL</constant> may be passed. Note that in the future | |
106 | additional categories may be defined. The second parameter returns | |
107 | a monitor object and needs to be freed with the | |
108 | <function>sd_login_monitor_unref()</function> call after | |
109 | use.</para> | |
110 | ||
111 | <para><function>sd_login_monitor_unref()</function> may be used to | |
112 | destroy a monitor object. Note that this will invalidate any file | |
113 | descriptor returned by | |
114 | <function>sd_login_monitor_get_fd()</function>.</para> | |
115 | ||
4afd3348 LP |
116 | <para><function>sd_login_monitor_unrefp()</function> is similar to |
117 | <function>sd_login_monitor_unref()</function> but takes a pointer | |
118 | to a pointer to an <type>sd_login_monitor</type> object. This call | |
119 | is useful in conjunction with GCC's and LLVM's <ulink | |
120 | url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up | |
121 | Variable Attribute</ulink>. Note that this function is defined as | |
122 | inline function. Use a declaration like the following, in order to | |
123 | allocate a login monitor object that is freed automatically as the | |
124 | code block is left:</para> | |
125 | ||
126 | <programlisting>{ | |
127 | __attribute__((cleanup(sd_login_monitor_unrefp)) sd_login_monitor *m = NULL; | |
128 | int r; | |
129 | … | |
130 | r = sd_login_monitor_default(&m); | |
131 | if (r < 0) | |
132 | fprintf(stderr, "Failed to allocate login monitor object: %s\n", strerror(-r)); | |
133 | … | |
134 | }</programlisting> | |
135 | ||
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136 | <para><function>sd_login_monitor_flush()</function> may be used to |
137 | reset the wakeup state of the monitor object. Whenever an event | |
138 | causes the monitor to wake up the event loop via the file | |
139 | descriptor this function needs to be called to reset the wake-up | |
140 | state. If this call is not invoked, the file descriptor will | |
141 | immediately wake up the event loop again.</para> | |
142 | ||
4afd3348 LP |
143 | <para><function>sd_login_monitor_unref()</function> and |
144 | <function>sd_login_monitor_unrefp()</function> execute no | |
145 | operation if the passed in monitor object is | |
146 | <constant>NULL</constant>.</para> | |
147 | ||
798d3a52 ZJS |
148 | <para><function>sd_login_monitor_get_fd()</function> may be used |
149 | to retrieve the file descriptor of the monitor object that may be | |
150 | integrated in an application defined event loop, based around | |
151 | <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
152 | or a similar interface. The application should include the | |
153 | returned file descriptor as wake-up source for the events mask | |
154 | returned by <function>sd_login_monitor_get_events()</function>. It | |
155 | should pass a timeout value as returned by | |
156 | <function>sd_login_monitor_get_timeout()</function>. Whenever a | |
157 | wake-up is triggered the file descriptor needs to be reset via | |
158 | <function>sd_login_monitor_flush()</function>. An application | |
159 | needs to reread the login state with a function like | |
160 | <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
161 | or similar to determine what changed.</para> | |
162 | ||
163 | <para><function>sd_login_monitor_get_events()</function> will | |
164 | return the <function>poll()</function> mask to wait for. This | |
165 | function will return a combination of <constant>POLLIN</constant>, | |
166 | <constant>POLLOUT</constant> and similar to fill into the | |
167 | <literal>.events</literal> field of <varname>struct | |
168 | pollfd</varname>.</para> | |
169 | ||
170 | <para><function>sd_login_monitor_get_timeout()</function> will | |
171 | return a timeout value for usage in <function>poll()</function>. | |
172 | This returns a value in microseconds since the epoch of | |
173 | <constant>CLOCK_MONOTONIC</constant> for timing out | |
174 | <function>poll()</function> in <varname>timeout_usec</varname>. | |
175 | See | |
176 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
177 | for details about <constant>CLOCK_MONOTONIC</constant>. If there | |
178 | is no timeout to wait for this will fill in <constant>(uint64_t) | |
179 | -1</constant> instead. Note that <function>poll()</function> takes | |
180 | a relative timeout in milliseconds rather than an absolute timeout | |
707b66c6 | 181 | in microseconds. To convert the absolute 'µs' timeout into |
798d3a52 ZJS |
182 | relative 'ms', use code like the following:</para> |
183 | ||
184 | <programlisting>uint64_t t; | |
667c24a6 LP |
185 | int msec; |
186 | sd_login_monitor_get_timeout(m, &t); | |
187 | if (t == (uint64_t) -1) | |
707b66c6 | 188 | msec = -1; |
667c24a6 | 189 | else { |
707b66c6 LP |
190 | struct timespec ts; |
191 | uint64_t n; | |
8feabc46 | 192 | clock_gettime(CLOCK_MONOTONIC, &ts); |
707b66c6 LP |
193 | n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000; |
194 | msec = t > n ? (int) ((t - n + 999) / 1000) : 0; | |
667c24a6 LP |
195 | }</programlisting> |
196 | ||
798d3a52 ZJS |
197 | <para>The code above does not do any error checking for brevity's |
198 | sake. The calculated <varname>msec</varname> integer can be passed | |
199 | directly as <function>poll()</function>'s timeout | |
200 | parameter.</para> | |
201 | </refsect1> | |
202 | ||
203 | <refsect1> | |
204 | <title>Return Value</title> | |
205 | ||
206 | <para>On success, | |
207 | <function>sd_login_monitor_new()</function>, | |
208 | <function>sd_login_monitor_flush()</function> and | |
209 | <function>sd_login_monitor_get_timeout()</function> | |
210 | return 0 or a positive integer. On success, | |
211 | <function>sd_login_monitor_get_fd()</function> returns | |
212 | a Unix file descriptor. On success, | |
213 | <function>sd_login_monitor_get_events()</function> | |
214 | returns a combination of <constant>POLLIN</constant>, | |
215 | <constant>POLLOUT</constant> and suchlike. On failure, | |
216 | these calls return a negative errno-style error | |
217 | code.</para> | |
218 | ||
219 | <para><function>sd_login_monitor_unref()</function> | |
220 | always returns <constant>NULL</constant>.</para> | |
221 | </refsect1> | |
222 | ||
707b66c6 LP |
223 | <refsect1> |
224 | <title>Errors</title> | |
225 | ||
226 | <para>Returned errors may indicate the following problems:</para> | |
227 | ||
228 | <variablelist> | |
229 | ||
230 | <varlistentry> | |
231 | <term><constant>-EINVAL</constant></term> | |
232 | ||
233 | <listitem><para>An input parameter was invalid (out of range, | |
7ca41557 | 234 | or NULL, where that is not accepted). The specified category to |
707b66c6 LP |
235 | watch is not known.</para></listitem> |
236 | </varlistentry> | |
237 | ||
238 | <varlistentry> | |
239 | <term><constant>-ENOMEM</constant></term> | |
240 | ||
241 | <listitem><para>Memory allocation failed.</para></listitem> | |
242 | </varlistentry> | |
243 | </variablelist> | |
244 | </refsect1> | |
245 | ||
7d6b2723 | 246 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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247 | |
248 | <refsect1> | |
249 | <title>See Also</title> | |
250 | ||
251 | <para> | |
252 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
253 | <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
254 | <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
255 | <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
256 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
257 | </para> | |
258 | </refsect1> | |
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259 | |
260 | </refentry> |