mirror of
https://github.com/systemd/systemd.git
synced 2024-11-05 06:52:22 +03:00
202 lines
8.4 KiB
XML
202 lines
8.4 KiB
XML
<?xml version='1.0'?>
|
|
<!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+ -->
|
|
|
|
<refentry id="sd_bus_new" xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>sd_bus_new</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>sd_bus_new</refentrytitle>
|
|
<manvolnum>3</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>sd_bus_new</refname>
|
|
<refname>sd_bus_ref</refname>
|
|
<refname>sd_bus_unref</refname>
|
|
<refname>sd_bus_unrefp</refname>
|
|
<refname>sd_bus_close_unref</refname>
|
|
<refname>sd_bus_close_unrefp</refname>
|
|
<refname>sd_bus_flush_close_unref</refname>
|
|
<refname>sd_bus_flush_close_unrefp</refname>
|
|
|
|
<refpurpose>Create a new bus object and create or destroy references to it</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_new</function></funcdef>
|
|
<paramdef>sd_bus **<parameter>bus</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>sd_bus *<function>sd_bus_ref</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>sd_bus *<function>sd_bus_unref</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>sd_bus *<function>sd_bus_close_unref</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>sd_bus *<function>sd_bus_flush_close_unref</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>void <function>sd_bus_unrefp</function></funcdef>
|
|
<paramdef>sd_bus **<parameter>busp</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>void <function>sd_bus_close_unrefp</function></funcdef>
|
|
<paramdef>sd_bus **<parameter>busp</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>void <function>sd_bus_flush_close_unrefp</function></funcdef>
|
|
<paramdef>sd_bus **<parameter>busp</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para><function>sd_bus_new()</function> creates a new bus
|
|
object. This object is reference-counted, and will be destroyed
|
|
when all references are gone. Initially, the caller of this
|
|
function owns the sole reference and the bus object will not be
|
|
connected to any bus. To connect it to a bus, make sure
|
|
to set an address with
|
|
<citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
or a related call, and then start the connection with
|
|
<citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
|
|
|
|
<para>In most cases, it is a better idea to invoke
|
|
<citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
or related calls instead of the more low-level
|
|
<function>sd_bus_new()</function> and
|
|
<function>sd_bus_start()</function>. The higher-level calls not
|
|
only allocate a bus object but also start the connection to a
|
|
well-known bus in a single function invocation.</para>
|
|
|
|
<para><function>sd_bus_ref()</function> increases the reference
|
|
counter of <parameter>bus</parameter> by one.</para>
|
|
|
|
<para><function>sd_bus_unref()</function> decreases the reference
|
|
counter of <parameter>bus</parameter> by one. Once the reference
|
|
count has dropped to zero, <parameter>bus</parameter> is destroyed
|
|
and cannot be used anymore, so further calls to
|
|
<function>sd_bus_ref()</function> or
|
|
<function>sd_bus_unref()</function> are illegal.</para>
|
|
|
|
<para><function>sd_bus_unrefp()</function> is similar to
|
|
<function>sd_bus_unref()</function> but takes a pointer to a
|
|
pointer to an <type>sd_bus</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 bus object that is freed automatically as the code
|
|
block is left:</para>
|
|
|
|
<programlisting>{
|
|
__attribute__((cleanup(sd_bus_unrefp))) sd_bus *bus = NULL;
|
|
int r;
|
|
…
|
|
r = sd_bus_default(&bus);
|
|
if (r < 0)
|
|
fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r));
|
|
…
|
|
}</programlisting>
|
|
|
|
<para><function>sd_bus_ref()</function> and <function>sd_bus_unref()</function>
|
|
execute no operation if the passed in bus object address is
|
|
<constant>NULL</constant>. <function>sd_bus_unrefp()</function> will first
|
|
dereference its argument, which must not be <constant>NULL</constant>, and will
|
|
execute no operation if <emphasis>that</emphasis> is <constant>NULL</constant>.
|
|
</para>
|
|
|
|
<para><function>sd_bus_close_unref()</function> is similar to <function>sd_bus_unref()</function>, but
|
|
first executes
|
|
<citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
ensuring that the connection is terminated before the reference to the connection is dropped and possibly
|
|
the object freed.</para>
|
|
|
|
<para><function>sd_bus_flush_close_unref()</function> is similar to <function>sd_bus_unref()</function>,
|
|
but first executes
|
|
<citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry> as well
|
|
as <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
ensuring that any pending messages are synchronously flushed out before the reference to the connection
|
|
is dropped and possibly the object freed. This call is particularly useful immediately before exiting
|
|
from a program as it ensures that any pending outgoing messages are written out, and unprocessed but
|
|
queued incoming messages released before the connection is terminated and released.</para>
|
|
|
|
<para><function>sd_bus_close_unrefp()</function> is similar to
|
|
<function>sd_bus_close_unref()</function>, but may be used in GCC's and LLVM's Clean-up Variable
|
|
Attribute, see above. Similarly, <function>sd_bus_flush_close_unrefp()</function> is similar to
|
|
<function>sd_bus_flush_close_unref()</function>.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Return Value</title>
|
|
|
|
<para>On success, <function>sd_bus_new()</function> returns 0 or a
|
|
positive integer. On failure, it returns a negative errno-style
|
|
error code.</para>
|
|
|
|
<para><function>sd_bus_ref()</function> always returns the argument.
|
|
</para>
|
|
|
|
<para><function>sd_bus_unref()</function> and <function>sd_bus_flush_close_unref()</function> always return
|
|
<constant>NULL</constant>.</para>
|
|
|
|
<refsect2>
|
|
<title>Errors</title>
|
|
|
|
<para>Returned errors may indicate the following problems:</para>
|
|
|
|
<variablelist>
|
|
<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-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_open_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_open_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|