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diff --git a/src/libsystemd/sd_login_monitor_new.xml b/src/libsystemd/sd_login_monitor_new.xml new file mode 100644 index 0000000000..5625ab9207 --- /dev/null +++ b/src/libsystemd/sd_login_monitor_new.xml @@ -0,0 +1,287 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + This file is part of systemd. + + Copyright 2010 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +--> + +<refentry id="sd_login_monitor_new" conditional='HAVE_PAM'> + + <refentryinfo> + <title>sd_login_monitor_new</title> + <productname>systemd</productname> + + <authorgroup> + <author> + <contrib>Developer</contrib> + <firstname>Lennart</firstname> + <surname>Poettering</surname> + <email>lennart@poettering.net</email> + </author> + </authorgroup> + </refentryinfo> + + <refmeta> + <refentrytitle>sd_login_monitor_new</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_login_monitor_new</refname> + <refname>sd_login_monitor_unref</refname> + <refname>sd_login_monitor_unrefp</refname> + <refname>sd_login_monitor_flush</refname> + <refname>sd_login_monitor_get_fd</refname> + <refname>sd_login_monitor_get_events</refname> + <refname>sd_login_monitor_get_timeout</refname> + <refname>sd_login_monitor</refname> + <refpurpose>Monitor login sessions, seats, users and virtual machines/containers</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-login.h></funcsynopsisinfo> + + <funcprototype> + <funcdef>int <function>sd_login_monitor_new</function></funcdef> + <paramdef>const char *<parameter>category</parameter></paramdef> + <paramdef>sd_login_monitor **<parameter>ret</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>sd_login_monitor *<function>sd_login_monitor_unref</function></funcdef> + <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>void <function>sd_login_monitor_unrefp</function></funcdef> + <paramdef>sd_login_monitor **<parameter>m</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_login_monitor_flush</function></funcdef> + <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_login_monitor_get_fd</function></funcdef> + <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_login_monitor_get_events</function></funcdef> + <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_login_monitor_get_timeout</function></funcdef> + <paramdef>sd_login_monitor *<parameter>m</parameter></paramdef> + <paramdef>uint64_t *<parameter>timeout_usec</parameter></paramdef> + </funcprototype> + + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><function>sd_login_monitor_new()</function> may be used to + monitor login sessions, users, seats, and virtual + machines/containers. Via a monitor object a file descriptor can be + integrated into an application defined event loop which is woken + up each time a user logs in, logs out or a seat is added or + removed, or a session, user, seat or virtual machine/container + changes state otherwise. The first parameter takes a string which + can be <literal>seat</literal> (to get only notifications about + seats being added, removed or changed), <literal>session</literal> + (to get only notifications about sessions being created or removed + or changed), <literal>uid</literal> (to get only notifications + when a user changes state in respect to logins) or + <literal>machine</literal> (to get only notifications when a + virtual machine or container is started or stopped). If + notifications shall be generated in all these conditions, + <constant>NULL</constant> may be passed. Note that in the future + additional categories may be defined. The second parameter returns + a monitor object and needs to be freed with the + <function>sd_login_monitor_unref()</function> call after + use.</para> + + <para><function>sd_login_monitor_unref()</function> may be used to + destroy a monitor object. Note that this will invalidate any file + descriptor returned by + <function>sd_login_monitor_get_fd()</function>.</para> + + <para><function>sd_login_monitor_unrefp()</function> is similar to + <function>sd_login_monitor_unref()</function> but takes a pointer + to a pointer to an <type>sd_login_monitor</type> object. This call + is useful in conjunction with GCC's and LLVM's <ulink + url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up + Variable Attribute</ulink>. Note that this function is defined as + inline function. Use a declaration like the following, in order to + allocate a login monitor object that is freed automatically as the + code block is left:</para> + + <programlisting>{ + __attribute__((cleanup(sd_login_monitor_unrefp)) sd_login_monitor *m = NULL; + int r; + … + r = sd_login_monitor_default(&m); + if (r < 0) + fprintf(stderr, "Failed to allocate login monitor object: %s\n", strerror(-r)); + … +}</programlisting> + + <para><function>sd_login_monitor_flush()</function> may be used to + reset the wakeup state of the monitor object. Whenever an event + causes the monitor to wake up the event loop via the file + descriptor this function needs to be called to reset the wake-up + state. If this call is not invoked, the file descriptor will + immediately wake up the event loop again.</para> + + <para><function>sd_login_monitor_unref()</function> and + <function>sd_login_monitor_unrefp()</function> execute no + operation if the passed in monitor object is + <constant>NULL</constant>.</para> + + <para><function>sd_login_monitor_get_fd()</function> may be used + to retrieve the file descriptor of the monitor object that may be + integrated in an application defined event loop, based around + <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry> + or a similar interface. The application should include the + returned file descriptor as wake-up source for the events mask + returned by <function>sd_login_monitor_get_events()</function>. It + should pass a timeout value as returned by + <function>sd_login_monitor_get_timeout()</function>. Whenever a + wake-up is triggered the file descriptor needs to be reset via + <function>sd_login_monitor_flush()</function>. An application + needs to reread the login state with a function like + <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry> + or similar to determine what changed.</para> + + <para><function>sd_login_monitor_get_events()</function> will + return the <function>poll()</function> mask to wait for. This + function will return a combination of <constant>POLLIN</constant>, + <constant>POLLOUT</constant> and similar to fill into the + <literal>.events</literal> field of <varname>struct + pollfd</varname>.</para> + + <para><function>sd_login_monitor_get_timeout()</function> will + return a timeout value for usage in <function>poll()</function>. + This returns a value in microseconds since the epoch of + <constant>CLOCK_MONOTONIC</constant> for timing out + <function>poll()</function> in <varname>timeout_usec</varname>. + See + <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> + for details about <constant>CLOCK_MONOTONIC</constant>. If there + is no timeout to wait for this will fill in <constant>(uint64_t) + -1</constant> instead. Note that <function>poll()</function> takes + a relative timeout in milliseconds rather than an absolute timeout + in microseconds. To convert the absolute 'µs' timeout into + relative 'ms', use code like the following:</para> + + <programlisting>uint64_t t; +int msec; +sd_login_monitor_get_timeout(m, &t); +if (t == (uint64_t) -1) + msec = -1; +else { + struct timespec ts; + uint64_t n; + clock_getttime(CLOCK_MONOTONIC, &ts); + n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000; + msec = t > n ? (int) ((t - n + 999) / 1000) : 0; +}</programlisting> + + <para>The code above does not do any error checking for brevity's + sake. The calculated <varname>msec</varname> integer can be passed + directly as <function>poll()</function>'s timeout + parameter.</para> + </refsect1> + + <refsect1> + <title>Return Value</title> + + <para>On success, + <function>sd_login_monitor_new()</function>, + <function>sd_login_monitor_flush()</function> and + <function>sd_login_monitor_get_timeout()</function> + return 0 or a positive integer. On success, + <function>sd_login_monitor_get_fd()</function> returns + a Unix file descriptor. On success, + <function>sd_login_monitor_get_events()</function> + returns a combination of <constant>POLLIN</constant>, + <constant>POLLOUT</constant> and suchlike. On failure, + these calls return a negative errno-style error + code.</para> + + <para><function>sd_login_monitor_unref()</function> + always returns <constant>NULL</constant>.</para> + </refsect1> + + <refsect1> + <title>Errors</title> + + <para>Returned errors may indicate the following problems:</para> + + <variablelist> + + <varlistentry> + <term><constant>-EINVAL</constant></term> + + <listitem><para>An input parameter was invalid (out of range, + or NULL, where that is not accepted). The specified category to + watch is not known.</para></listitem> + </varlistentry> + + <varlistentry> + <term><constant>-ENOMEM</constant></term> + + <listitem><para>Memory allocation failed.</para></listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Notes</title> + + <para>The <function>sd_login_monitor_new()</function>, + <function>sd_login_monitor_unref()</function>, + <function>sd_login_monitor_flush()</function>, + <function>sd_login_monitor_get_fd()</function>, + <function>sd_login_monitor_get_events()</function> and + <function>sd_login_monitor_get_timeout()</function> + interfaces are available as a shared library, which can be + compiled and linked to with the + <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> + file.</para> + </refsect1> + + <refsect1> + <title>See Also</title> + + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>, + <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |