mirror of
https://github.com/systemd/systemd
synced 2024-09-06 16:56:43 +00:00
![Zbigniew Jędrzejewski-Szmek](/assets/img/avatar_default.png)
The need to set errno is very very ugly, but at least it is thread-safe and works correctly. Using strerror() is likely to be wrong, so let's not recommend that. People who do a lot of logging would provide use some wrapper that sets errno like we do, so nudge people towards %m. I tested that all the separate .c files compile cleanly.
250 lines
10 KiB
XML
250 lines
10 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
|
|
|
|
<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>
|
|
</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_new(NULL, &m);
|
|
if (r < 0) {
|
|
errno = -r;
|
|
fprintf(stderr, "Failed to allocate login monitor object: %m\n");
|
|
}
|
|
…
|
|
}</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_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
|
|
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>
|
|
|
|
<refsect2>
|
|
<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 <constant>NULL</constant>, 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>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<xi:include href="libsystemd-pkgconfig.xml" />
|
|
|
|
<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>
|