"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/>.
+ SPDX-License-Identifier: LGPL-2.1+
-->
-<refentry id="sd_login_monitor_new" conditional='HAVE_PAM'>
+<refentry id="sd_login_monitor_new" conditional='HAVE_PAM'
+ xmlns:xi="http://www.w3.org/2001/XInclude">
<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>
<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>
<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>
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
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
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 'us' timeout into
+ 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;
+ 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;
+ struct timespec ts;
+ uint64_t n;
+ clock_gettime(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
</refsect1>
<refsect1>
- <title>Notes</title>
+ <title>Errors</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>libelogind</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- file.</para>
+ <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>
+ <xi:include href="libelogind-pkgconfig.xml" />
+
<refsect1>
<title>See Also</title>
~ianmdlvl / elogind.git / blobdiff