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0b3b020a | 1 | <?xml version='1.0'?> <!--*-nxml-*--> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
0307f791 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
0b3b020a | 5 | |
7d6b2723 ZJS |
6 | <refentry id="sd_login_monitor_new" conditional='HAVE_PAM' |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
0b3b020a | 8 | |
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9 | <refentryinfo> |
10 | <title>sd_login_monitor_new</title> | |
11 | <productname>systemd</productname> | |
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12 | </refentryinfo> |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>sd_login_monitor_new</refentrytitle> | |
16 | <manvolnum>3</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>sd_login_monitor_new</refname> | |
21 | <refname>sd_login_monitor_unref</refname> | |
4afd3348 | 22 | <refname>sd_login_monitor_unrefp</refname> |
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23 | <refname>sd_login_monitor_flush</refname> |
24 | <refname>sd_login_monitor_get_fd</refname> | |
25 | <refname>sd_login_monitor_get_events</refname> | |
26 | <refname>sd_login_monitor_get_timeout</refname> | |
27 | <refname>sd_login_monitor</refname> | |
28 | <refpurpose>Monitor login sessions, seats, users and virtual machines/containers</refpurpose> | |
29 | </refnamediv> | |
30 | ||
31 | <refsynopsisdiv> | |
32 | <funcsynopsis> | |
33 | <funcsynopsisinfo>#include <systemd/sd-login.h></funcsynopsisinfo> | |
34 | ||
35 | <funcprototype> | |
36 | <funcdef>int <function>sd_login_monitor_new</function></funcdef> | |
37 | <paramdef>const char *<parameter>category</parameter></paramdef> | |
38 | <paramdef>sd_login_monitor **<parameter>ret</parameter></paramdef> | |
39 | </funcprototype> | |
40 | ||
41 | <funcprototype> | |
42 | <funcdef>sd_login_monitor *<function>sd_login_monitor_unref</function></funcdef> | |
43 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
44 | </funcprototype> | |
45 | ||
4afd3348 LP |
46 | <funcprototype> |
47 | <funcdef>void <function>sd_login_monitor_unrefp</function></funcdef> | |
48 | <paramdef>sd_login_monitor **<parameter>m</parameter></paramdef> | |
49 | </funcprototype> | |
50 | ||
798d3a52 ZJS |
51 | <funcprototype> |
52 | <funcdef>int <function>sd_login_monitor_flush</function></funcdef> | |
53 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
54 | </funcprototype> | |
55 | ||
56 | <funcprototype> | |
57 | <funcdef>int <function>sd_login_monitor_get_fd</function></funcdef> | |
58 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
59 | </funcprototype> | |
60 | ||
61 | <funcprototype> | |
62 | <funcdef>int <function>sd_login_monitor_get_events</function></funcdef> | |
63 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
64 | </funcprototype> | |
65 | ||
66 | <funcprototype> | |
67 | <funcdef>int <function>sd_login_monitor_get_timeout</function></funcdef> | |
68 | <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> | |
69 | <paramdef>uint64_t *<parameter>timeout_usec</parameter></paramdef> | |
70 | </funcprototype> | |
71 | ||
72 | </funcsynopsis> | |
73 | </refsynopsisdiv> | |
74 | ||
75 | <refsect1> | |
76 | <title>Description</title> | |
77 | ||
78 | <para><function>sd_login_monitor_new()</function> may be used to | |
79 | monitor login sessions, users, seats, and virtual | |
80 | machines/containers. Via a monitor object a file descriptor can be | |
81 | integrated into an application defined event loop which is woken | |
82 | up each time a user logs in, logs out or a seat is added or | |
83 | removed, or a session, user, seat or virtual machine/container | |
84 | changes state otherwise. The first parameter takes a string which | |
85 | can be <literal>seat</literal> (to get only notifications about | |
86 | seats being added, removed or changed), <literal>session</literal> | |
87 | (to get only notifications about sessions being created or removed | |
88 | or changed), <literal>uid</literal> (to get only notifications | |
89 | when a user changes state in respect to logins) or | |
90 | <literal>machine</literal> (to get only notifications when a | |
91 | virtual machine or container is started or stopped). If | |
92 | notifications shall be generated in all these conditions, | |
93 | <constant>NULL</constant> may be passed. Note that in the future | |
94 | additional categories may be defined. The second parameter returns | |
95 | a monitor object and needs to be freed with the | |
96 | <function>sd_login_monitor_unref()</function> call after | |
97 | use.</para> | |
98 | ||
99 | <para><function>sd_login_monitor_unref()</function> may be used to | |
100 | destroy a monitor object. Note that this will invalidate any file | |
101 | descriptor returned by | |
102 | <function>sd_login_monitor_get_fd()</function>.</para> | |
103 | ||
4afd3348 LP |
104 | <para><function>sd_login_monitor_unrefp()</function> is similar to |
105 | <function>sd_login_monitor_unref()</function> but takes a pointer | |
106 | to a pointer to an <type>sd_login_monitor</type> object. This call | |
107 | is useful in conjunction with GCC's and LLVM's <ulink | |
108 | url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up | |
109 | Variable Attribute</ulink>. Note that this function is defined as | |
110 | inline function. Use a declaration like the following, in order to | |
111 | allocate a login monitor object that is freed automatically as the | |
112 | code block is left:</para> | |
113 | ||
114 | <programlisting>{ | |
f4e1a425 | 115 | __attribute__((cleanup(sd_login_monitor_unrefp))) sd_login_monitor *m = NULL; |
787f78b6 ZJS |
116 | int r; |
117 | … | |
118 | r = sd_login_monitor_default(&m); | |
119 | if (r < 0) | |
120 | fprintf(stderr, "Failed to allocate login monitor object: %s\n", strerror(-r)); | |
121 | … | |
4afd3348 LP |
122 | }</programlisting> |
123 | ||
798d3a52 ZJS |
124 | <para><function>sd_login_monitor_flush()</function> may be used to |
125 | reset the wakeup state of the monitor object. Whenever an event | |
126 | causes the monitor to wake up the event loop via the file | |
127 | descriptor this function needs to be called to reset the wake-up | |
128 | state. If this call is not invoked, the file descriptor will | |
129 | immediately wake up the event loop again.</para> | |
130 | ||
4afd3348 LP |
131 | <para><function>sd_login_monitor_unref()</function> and |
132 | <function>sd_login_monitor_unrefp()</function> execute no | |
133 | operation if the passed in monitor object is | |
134 | <constant>NULL</constant>.</para> | |
135 | ||
798d3a52 ZJS |
136 | <para><function>sd_login_monitor_get_fd()</function> may be used |
137 | to retrieve the file descriptor of the monitor object that may be | |
138 | integrated in an application defined event loop, based around | |
139 | <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
140 | or a similar interface. The application should include the | |
141 | returned file descriptor as wake-up source for the events mask | |
142 | returned by <function>sd_login_monitor_get_events()</function>. It | |
143 | should pass a timeout value as returned by | |
144 | <function>sd_login_monitor_get_timeout()</function>. Whenever a | |
145 | wake-up is triggered the file descriptor needs to be reset via | |
146 | <function>sd_login_monitor_flush()</function>. An application | |
147 | needs to reread the login state with a function like | |
148 | <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
149 | or similar to determine what changed.</para> | |
150 | ||
151 | <para><function>sd_login_monitor_get_events()</function> will | |
152 | return the <function>poll()</function> mask to wait for. This | |
153 | function will return a combination of <constant>POLLIN</constant>, | |
154 | <constant>POLLOUT</constant> and similar to fill into the | |
155 | <literal>.events</literal> field of <varname>struct | |
156 | pollfd</varname>.</para> | |
157 | ||
158 | <para><function>sd_login_monitor_get_timeout()</function> will | |
159 | return a timeout value for usage in <function>poll()</function>. | |
160 | This returns a value in microseconds since the epoch of | |
161 | <constant>CLOCK_MONOTONIC</constant> for timing out | |
162 | <function>poll()</function> in <varname>timeout_usec</varname>. | |
163 | See | |
164 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
165 | for details about <constant>CLOCK_MONOTONIC</constant>. If there | |
166 | is no timeout to wait for this will fill in <constant>(uint64_t) | |
167 | -1</constant> instead. Note that <function>poll()</function> takes | |
168 | a relative timeout in milliseconds rather than an absolute timeout | |
707b66c6 | 169 | in microseconds. To convert the absolute 'µs' timeout into |
798d3a52 ZJS |
170 | relative 'ms', use code like the following:</para> |
171 | ||
172 | <programlisting>uint64_t t; | |
667c24a6 LP |
173 | int msec; |
174 | sd_login_monitor_get_timeout(m, &t); | |
175 | if (t == (uint64_t) -1) | |
787f78b6 | 176 | msec = -1; |
667c24a6 | 177 | else { |
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178 | struct timespec ts; |
179 | uint64_t n; | |
180 | clock_gettime(CLOCK_MONOTONIC, &ts); | |
181 | n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000; | |
182 | msec = t > n ? (int) ((t - n + 999) / 1000) : 0; | |
667c24a6 LP |
183 | }</programlisting> |
184 | ||
798d3a52 ZJS |
185 | <para>The code above does not do any error checking for brevity's |
186 | sake. The calculated <varname>msec</varname> integer can be passed | |
187 | directly as <function>poll()</function>'s timeout | |
188 | parameter.</para> | |
189 | </refsect1> | |
190 | ||
191 | <refsect1> | |
192 | <title>Return Value</title> | |
193 | ||
194 | <para>On success, | |
195 | <function>sd_login_monitor_new()</function>, | |
196 | <function>sd_login_monitor_flush()</function> and | |
197 | <function>sd_login_monitor_get_timeout()</function> | |
198 | return 0 or a positive integer. On success, | |
199 | <function>sd_login_monitor_get_fd()</function> returns | |
200 | a Unix file descriptor. On success, | |
201 | <function>sd_login_monitor_get_events()</function> | |
202 | returns a combination of <constant>POLLIN</constant>, | |
203 | <constant>POLLOUT</constant> and suchlike. On failure, | |
204 | these calls return a negative errno-style error | |
205 | code.</para> | |
206 | ||
207 | <para><function>sd_login_monitor_unref()</function> | |
208 | always returns <constant>NULL</constant>.</para> | |
798d3a52 | 209 | |
b1de39de ZJS |
210 | <refsect2> |
211 | <title>Errors</title> | |
707b66c6 | 212 | |
b1de39de | 213 | <para>Returned errors may indicate the following problems:</para> |
707b66c6 | 214 | |
b1de39de | 215 | <variablelist> |
707b66c6 | 216 | |
b1de39de ZJS |
217 | <varlistentry> |
218 | <term><constant>-EINVAL</constant></term> | |
707b66c6 | 219 | |
b1de39de ZJS |
220 | <listitem><para>An input parameter was invalid (out of range, or <constant>NULL</constant>, where |
221 | that is not accepted). The specified category to watch is not known.</para></listitem> | |
222 | </varlistentry> | |
707b66c6 | 223 | |
b1de39de ZJS |
224 | <varlistentry> |
225 | <term><constant>-ENOMEM</constant></term> | |
707b66c6 | 226 | |
b1de39de ZJS |
227 | <listitem><para>Memory allocation failed.</para></listitem> |
228 | </varlistentry> | |
229 | </variablelist> | |
230 | </refsect2> | |
707b66c6 LP |
231 | </refsect1> |
232 | ||
7d6b2723 | 233 | <xi:include href="libsystemd-pkgconfig.xml" /> |
798d3a52 ZJS |
234 | |
235 | <refsect1> | |
236 | <title>See Also</title> | |
237 | ||
238 | <para> | |
239 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
240 | <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
241 | <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
242 | <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
243 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
244 | </para> | |
245 | </refsect1> | |
0b3b020a LP |
246 | |
247 | </refentry> |