mirror of
https://github.com/systemd/systemd-stable.git
synced 2024-12-23 17:34:00 +03:00
264 lines
13 KiB
XML
264 lines
13 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
|
||
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
||
|
||
<!--
|
||
SPDX-License-Identifier: LGPL-2.1+
|
||
|
||
This file is part of systemd.
|
||
|
||
Copyright 2016 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_bus_track_add_name">
|
||
|
||
<refentryinfo>
|
||
<title>sd_bus_track_add_name</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_bus_track_add_name</refentrytitle>
|
||
<manvolnum>3</manvolnum>
|
||
</refmeta>
|
||
|
||
<refnamediv>
|
||
<refname>sd_bus_track_add_name</refname>
|
||
<refname>sd_bus_track_add_sender</refname>
|
||
<refname>sd_bus_track_remove_name</refname>
|
||
<refname>sd_bus_track_remove_sender</refname>
|
||
<refname>sd_bus_track_count</refname>
|
||
<refname>sd_bus_track_count_sender</refname>
|
||
<refname>sd_bus_track_count_name</refname>
|
||
<refname>sd_bus_track_contains</refname>
|
||
<refname>sd_bus_track_first</refname>
|
||
<refname>sd_bus_track_next</refname>
|
||
|
||
<refpurpose>Add, remove and retrieve bus peers tracked in a bus peer tracking object</refpurpose>
|
||
</refnamediv>
|
||
|
||
<refsynopsisdiv>
|
||
<funcsynopsis>
|
||
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_add_name</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
<paramdef>const char* <parameter>name</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_add_sender</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
<paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_remove_name</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
<paramdef>const char* <parameter>name</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_remove_sender</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
<paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>unsigned <function>sd_bus_track_count</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_count_name</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
<paramdef>const char* <parameter>name</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_count_sender</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
<paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_contains</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
<paramdef>const char* <parameter>name</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>const char* <function>sd_bus_track_first</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>const char* <function>sd_bus_track_next</function></funcdef>
|
||
<paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
</funcsynopsis>
|
||
</refsynopsisdiv>
|
||
|
||
<refsect1>
|
||
<title>Description</title>
|
||
|
||
<para><function>sd_bus_track_add_name()</function> adds a peer to track to a bus peer tracking object. The first
|
||
argument should refer to a bus peer tracking object created with
|
||
<citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, the second
|
||
name should refer to a D-Bus peer name to track, either in unique or well-known service format. If the name is not
|
||
tracked yet it will be added to the list of names to track. If it already is being tracked and non-recursive mode
|
||
is enabled, no operation is executed by this call. If recursive mode is enabled a per-name counter is increased by
|
||
one each time this call is invoked, and <function>sd_bus_track_remove_name()</function> has to be called as many
|
||
times as <function>sd_bus_track_add_name()</function> was invoked before in order to stop tracking of the name. Use
|
||
<citerefentry><refentrytitle>sd_bus_track_set_recursive</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
|
||
switch from the default non-recursive mode to recursive mode, or back. Note that the specified name is tracked as
|
||
it is, well-known names are not resolved to unique names by this call. Note that multiple bus peer tracking objects
|
||
may track the same name.</para>
|
||
|
||
<para><function>sd_bus_track_remove_name()</function> undoes the effect of
|
||
<function>sd_bus_track_add_name()</function> and removes a bus peer name from the list of peers to watch. Depending
|
||
on whether non-recursive or recursive mode is enabled for the bus peer tracking object this call will either remove
|
||
the name fully from the tracking object, or will simply decrement the per-name counter by one, removing the name
|
||
only when the counter reaches zero (see above). Note that a bus peer disconnecting from the bus will implicitly
|
||
remove its names fully from the bus peer tracking object, regardless of the current per-name counter.</para>
|
||
|
||
<para><function>sd_bus_track_add_sender()</function> and <function>sd_bus_track_remove_sender()</function> are
|
||
similar to <function>sd_bus_track_add_name()</function> and <function>sd_bus_track_remove_name()</function> but
|
||
take a bus message as argument. The sender of this bus message is determined and added to/removed from the bus peer
|
||
tracking object. As messages always originate from unique names, and never from well-known names this means that
|
||
this call will effectively only add unique names to the bus peer tracking object.</para>
|
||
|
||
<para><function>sd_bus_track_count()</function> returns the number of names currently being tracked by the
|
||
specified bus peer tracking object. Note that this function always returns the actual number of names tracked, and
|
||
hence if <function>sd_bus_track_add_name()</function> has been invoked multiple times for the same name it is only
|
||
counted as one, regardless if recursive mode is used or not.</para>
|
||
|
||
<para><function>sd_bus_track_count_name()</function> returns the current per-name counter for the specified
|
||
name. If non-recursive mode is used this returns either 1 or 0, depending on whether the specified name has been
|
||
added to the tracking object before, or not. If recursive mode has been enabled, values larger than 1 may be
|
||
returned too, in case <function>sd_bus_track_add_name()</function> has been called multiple times for the same
|
||
name.</para>
|
||
|
||
<para><function>sd_bus_track_count_sender()</function> is similar to
|
||
<function>sd_bus_track_count_name()</function>, but takes a bus message object and returns the per-name counter
|
||
matching the sender of the message.</para>
|
||
|
||
<para><function>sd_bus_track_contains()</function> may be used to determine whether the specified name has been
|
||
added at least once to the specified bus peer tracking object.</para>
|
||
|
||
<para><function>sd_bus_track_first()</function> and <function>sd_bus_track_next()</function> may be used to
|
||
enumerate all names currently being tracked by the passed bus peer tracking
|
||
object. <function>sd_bus_track_first()</function> returns the first entry in the object, and resets an internally
|
||
maintained read index. Each subsequent invocation of <function>sd_bus_track_next()</function> returns the next name
|
||
contained in the bus object. If the end is reached <constant>NULL</constant> is returned. If no names have been
|
||
added to the object yet <function>sd_bus_track_first()</function> will return <constant>NULL</constant>
|
||
immediately. The order in which names are returned is undefined; in particular which name is considered the first
|
||
returned is not defined. If recursive mode is enabled and the same name has been added multiple times to the bus
|
||
peer tracking object it is only returned once by this enumeration. If new names are added to or existing names
|
||
removed from the bus peer tracking object while it is being enumerated the enumeration ends on the next invocation
|
||
of <function>sd_bus_track_next()</function> as <constant>NULL</constant> is returned.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Return Value</title>
|
||
|
||
<para>On success, <function>sd_bus_track_add_name()</function> and <function>sd_bus_track_add_sender()</function>
|
||
return 0 if the specified name has already been added to the bus peer tracking object before and positive if it
|
||
hasn't. On failure, they return a negative errno-style error code.</para>
|
||
|
||
<para><function>sd_bus_track_remove_name()</function> and <function>sd_bus_track_remove_sender()</function> return
|
||
positive if the specified name was previously tracked by the bus peer tracking object and has now been removed. In
|
||
non-recursive mode, 0 is returned if the specified name was not being tracked yet. In recursive mode
|
||
<constant>-EUNATCH</constant> is returned in this case. On failure, they return a negative errno-style error
|
||
code.</para>
|
||
|
||
<para><function>sd_bus_track_count()</function> returns the number of names currently being tracked, or 0 on
|
||
failure.</para>
|
||
|
||
<para><function>sd_bus_track_count_name()</function> and <function>sd_bus_track_count_sender()</function> return
|
||
the current per-name counter for the specified name or the sender of the specified message. Zero is returned for
|
||
names that are not being tracked yet, a positive value for names added at least once. Larger values than 1 are only
|
||
returned in recursive mode. On failure, a negative errno-style error code is returned.</para>
|
||
|
||
<para><function>sd_bus_track_contains()</function> returns the passed name if it exists in the bus peer tracking
|
||
object. On failure, and if the name has not been added yet <constant>NULL</constant> is returned.</para>
|
||
|
||
<para><function>sd_bus_track_first()</function> and <function>sd_bus_track_next()</function> return the first/next
|
||
name contained in the bus peer tracking object, and <constant>NULL</constant> if the end of the enumeration is
|
||
reached and on error.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Errors</title>
|
||
|
||
<para>Returned errors may indicate the following problems:</para>
|
||
|
||
<variablelist>
|
||
|
||
<varlistentry>
|
||
<term><constant>-EUNATCH</constant></term>
|
||
|
||
<listitem><para><function>sd_bus_track_remove_name()</function> or
|
||
<function>sd_bus_track_remove_sender()</function> have been invoked for a name not previously added to the bus
|
||
peer object.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><constant>-EINVAL</constant></term>
|
||
|
||
<listitem><para>Specified parameter is invalid.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><constant>-ENOMEM</constant></term>
|
||
|
||
<listitem><para>Memory allocation failed.</para></listitem>
|
||
</varlistentry>
|
||
|
||
</variablelist>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Notes</title>
|
||
|
||
<para><function>sd_bus_track_add_name()</function> and the other calls described here 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-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|