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11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
179 lines
6.5 KiB
XML
179 lines
6.5 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2014 Zbigniew Jędrzejewski-Szmek
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-->
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<refentry id="sd_bus_new">
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<refentryinfo>
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<title>sd_bus_new</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>A monkey with a typewriter</contrib>
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<firstname>Zbigniew</firstname>
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<surname>Jędrzejewski-Szmek</surname>
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<email>zbyszek@in.waw.pl</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_new</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_bus_new</refname>
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<refname>sd_bus_ref</refname>
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<refname>sd_bus_unref</refname>
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<refname>sd_bus_unrefp</refname>
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<refpurpose>Create a new bus object and create or destroy references to it</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_bus_new</function></funcdef>
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<paramdef>sd_bus **<parameter>bus</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus *<function>sd_bus_ref</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus *<function>sd_bus_unref</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_bus_unrefp</function></funcdef>
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<paramdef>sd_bus **<parameter>bus</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_bus_new()</function> creates a new bus
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object. This object is reference-counted, and will be destroyed
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when all references are gone. Initially, the caller of this
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function owns the sole reference and the bus object will not be
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connected to any bus. To connect it to a bus, make sure
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to set an address with
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<citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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or a related call, and then start the connection with
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<citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>In most cases, it is a better idea to invoke
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<citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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or related calls instead of the more low-level
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<function>sd_bus_new()</function> and
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<function>sd_bus_start()</function>. The higher-level calls not
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only allocate a bus object but also start the connection to a
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well-known bus in a single function invocation.</para>
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<para><function>sd_bus_ref()</function> increases the reference
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counter of <parameter>bus</parameter> by one.</para>
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<para><function>sd_bus_unref()</function> decreases the reference
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counter of <parameter>bus</parameter> by one. Once the reference
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count has dropped to zero, <parameter>bus</parameter> is destroyed
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and cannot be used anymore, so further calls to
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<function>sd_bus_ref()</function> or
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<function>sd_bus_unref()</function> are illegal.</para>
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<para><function>sd_bus_unrefp()</function> is similar to
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<function>sd_bus_unref()</function> but takes a pointer to a
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pointer to an <type>sd_bus</type> object. This call is useful in
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conjunction with GCC's and LLVM's <ulink
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url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
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Variable Attribute</ulink>. Note that this function is defined as
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inline function. Use a declaration like the following, in order to
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allocate a bus object that is freed automatically as the code
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block is left:</para>
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<programlisting>{
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__attribute__((cleanup(sd_bus_unrefp)) sd_bus *bus = NULL;
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int r;
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…
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r = sd_bus_default(&bus);
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if (r < 0)
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fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r));
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…
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}</programlisting>
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<para><function>sd_bus_ref()</function>,
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<function>sd_bus_unref()</function> and
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<function>sd_bus_unrefp()</function> execute no operation if the
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passed in bus object is <constant>NULL</constant>.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>sd_bus_new()</function> returns 0 or a
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positive integer. On failure, it returns a negative errno-style
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error code.</para>
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<para><function>sd_bus_ref()</function> always returns the argument.
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</para>
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<para><function>sd_bus_unref()</function> always returns
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<constant>NULL</constant>.</para>
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</refsect1>
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<refsect1>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-ENOMEM</constant></term>
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<listitem><para>Memory allocation failed.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para><function>sd_bus_new()</function> and other functions
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described here are available as a shared library, which can be
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compiled and linked to with the
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<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_open_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_open_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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