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deb480d1a7
Either it is shared across threads, or it is per-thread: decide. Reading the source code, I see a thread_local identifier, so that's that. But that does not yet preclude that a program may pass around the pointer returned from the function among its own threads. Do a best effort at saying so.
218 lines
8.2 KiB
XML
218 lines
8.2 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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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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This file is part of systemd.
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Copyright 2014 Zbigniew Jędrzejewski-Szmek
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_bus_open_user">
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<refentryinfo>
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<title>sd_bus_open_user</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_open_user</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_open_user</refname>
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<refname>sd_bus_open_system</refname>
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<refname>sd_bus_open_system_remote</refname>
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<refname>sd_bus_open_system_container</refname>
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<refname>sd_bus_default_user</refname>
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<refname>sd_bus_default_system</refname>
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<refpurpose>Open a connection to the system or user bus</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_open_user</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>int <function>sd_bus_open_system</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>int <function>sd_bus_open_system_remote</function></funcdef>
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<paramdef>const char *<parameter>host</parameter></paramdef>
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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>int <function>sd_bus_open_system_container</function></funcdef>
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<paramdef>const char *<parameter>machine</parameter></paramdef>
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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>int <function>sd_bus_default_user</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>int <function>sd_bus_default_system</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_open_user()</function> creates a new bus
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object and opens a connection to the the user bus.
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<function>sd_bus_open_system()</function> does the same, but
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connects to the system bus.</para>
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<para>If the <varname>$DBUS_SESSION_BUS_ADDRESS</varname> environment
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variable is set
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(c.f. <citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>),
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it will be used as the address of the user bus. This variable can
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contain multiple addresses separated by <literal>;</literal>. If
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this variable is not set, a suitable default for the default user
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D-Bus instance will be used.</para>
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<para>If the <varname>$DBUS_SYSTEM_BUS_ADDRESS</varname> environment
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variable is set, it will be used as the address of the system
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bus. This variable uses the same syntax as
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<varname>$DBUS_SESSION_BUS_ADDRESS</varname>/. If this variable is
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not set, a suitable default for the default system D-Bus instance
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will be used.</para>
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<para><function>sd_bus_open_system_remote()</function> connects to
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the system bus on the specified <parameter>host</parameter> using
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SSH. <parameter>host</parameter> consists of an optional user name
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followed by the <literal>@</literal> symbol, and the hostname.
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</para>
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<para><function>sd_bus_open_system_remote()</function> connects to
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the system bus in the specified <parameter>machine</parameter>,
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where <parameter>machine</parameter> is the name of a container.
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See
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<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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for more information about "machines".</para>
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<para><function>sd_bus_default_user()</function> returns a bus
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object connected to the user bus. Each thread has its own object, but it
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may be passed around. It is created on the first invocation of
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<function>sd_bus_default_user()</function>, and subsequent
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invocations returns a reference to the same object.</para>
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<para><function>sd_bus_default_system()</function> is similar to
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<function>sd_bus_default_user()</function>, but connects to the
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system bus.</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, these calls return 0 or a positive
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integer. On failure, these calls return a negative
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errno-style error code.</para>
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</refsect1>
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<refsect1>
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<title>Reference ownership</title>
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<para>Functions <function>sd_bus_open_user()</function>,
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<function>sd_bus_open_system()</function>,
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<function>sd_bus_open_system_remote()</function>, and
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<function>sd_bus_open_system_machine()</function> return a new
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object and the caller owns the sole reference. When not needed
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anymore, this reference should be destroyed with
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<citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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</para>
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<para>The functions <function>sd_bus_default_user()</function> and
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<function>sd_bus_default_system()</function> do not create a new
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reference.</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><varname>-EINVAL</varname></term>
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<listitem><para>Specified parameter is invalid
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(<constant>NULL</constant> in case of output
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parameters).</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>-ENOMEM</varname></term>
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<listitem><para>Memory allocation failed.</para></listitem>
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</varlistentry>
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<para>In addition, any further connection-related errors may be
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by returned. See <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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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_open_user()</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><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_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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