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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.
203 lines
9.1 KiB
XML
203 lines
9.1 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_message_append_array"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_message_append_array</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_message_append_array</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_message_append_array</refname>
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<refname>sd_bus_message_append_array_memfd</refname>
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<refname>sd_bus_message_append_array_iovec</refname>
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<refname>sd_bus_message_append_array_space</refname>
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<refpurpose>Append an array of fields to a D-Bus
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message</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 sd_bus_message_append_array</funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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<paramdef>char <parameter>type</parameter></paramdef>
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<paramdef>char void *<parameter>ptr</parameter></paramdef>
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<paramdef>size_t <parameter>size</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int sd_bus_message_append_array_memfd</funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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<paramdef>char <parameter>type</parameter></paramdef>
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<paramdef>int <parameter>memfd</parameter></paramdef>
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<paramdef>uint64_t <parameter>offset</parameter></paramdef>
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<paramdef>uint64_t <parameter>size</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int sd_bus_message_append_array_iovec</funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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<paramdef>char <parameter>type</parameter></paramdef>
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<paramdef>const struct iovec *<parameter>iov</parameter></paramdef>
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<paramdef>unsigned <parameter>n</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int sd_bus_message_append_array_space</funcdef>
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<paramdef>char <parameter>type</parameter></paramdef>
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<paramdef>size_t <parameter>size</parameter></paramdef>
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<paramdef>void **<parameter>ptr</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>The <function>sd_bus_message_append_array()</function>
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function appends an array to a D-Bus message
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<parameter>m</parameter>. A container will be opened, the array
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contents appended, and the container closed. The parameter
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<parameter>type</parameter> determines how the pointer
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<parameter>p</parameter> is interpreted.
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<parameter>type</parameter> must be one of the "trivial" types
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<literal>y</literal>, <literal>n</literal>, <literal>q</literal>,
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<literal>i</literal>, <literal>u</literal>, <literal>x</literal>,
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<literal>t</literal>, <literal>d</literal> (but not
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<literal>b</literal>), as defined by the <ulink
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url="http://dbus.freedesktop.org/doc/dbus-specification.html#basic-types">Basic
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Types</ulink> section of the D-Bus specification, and listed in
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<citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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Pointer <parameter>p</parameter> must point to an array of size
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<parameter>size</parameter> bytes containing items of the
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respective type. Size <parameter>size</parameter> must be a
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multiple of the size of the type <parameter>type</parameter>. As a
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special case, <parameter>p</parameter> may be
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<constant>NULL</constant>, if <parameter>size</parameter> is 0.
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The memory pointed to by <parameter>p</parameter> is copied into
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the memory area containing the message and stays in possession of
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the caller. The caller may hence freely change the data after this
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call without affecting the message the array was appended
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to.</para>
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<para>The <function>sd_bus_message_append_array_memfd()</function>
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function appends an array of a trivial type to message
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<parameter>m</parameter>, similar to
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<function>sd_bus_message_append_array()</function>. The contents
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of the memory file descriptor <parameter>memfd</parameter>
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starting at the specified offset and of the specified size is
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used as the contents of the array. The offset and size must be a
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multiple of the size of the type
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<parameter>type</parameter>. However, as a special exception, if
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the offset is specified as zero and the size specified as
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UINT64_MAX the full memory file descriptor contents is used. The
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memory file descriptor is sealed by this call if it has not been
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sealed yet, and cannot be modified after this call. See
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<citerefentry
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project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details about memory file descriptors. Appending arrays with
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memory file descriptors enables efficient zero-copy data transfer,
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as the memory file descriptor may be passed as-is to the
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destination, without copying the memory in it to the destination
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process. Not all protocol transports support passing memory file
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descriptors between participants, in which case this call will
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automatically fall back to copying. Also, as memory file
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descriptor passing is inefficient for smaller amounts of data,
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copying might still be enforced even where memory file descriptor
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passing is supported.</para>
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<para>The <function>sd_bus_message_append_array_iovec()</function>
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function appends an array of a trivial type to the message
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<parameter>m</parameter>, similar to
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<function>sd_bus_message_append_array()</function>. Contents of
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the I/O vector array <parameter>iov</parameter> are used as the
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contents of the array. The total size of
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<parameter>iov</parameter> payload (the sum of
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<structfield>iov_len</structfield> fields) must be a multiple of
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the size of the type <parameter>type</parameter>. The
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<parameter>iov</parameter> argument must point to
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<parameter>n</parameter> I/O vector structures. Each structure may
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have the <structname>iov_base</structname> field set, in which
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case the memory pointed to will be copied into the message, or
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unset (set to zero), in which case a block of zeros of length
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<structname>iov_len</structname> bytes will be inserted. The
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memory pointed at by <parameter>iov</parameter> may be changed
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after this call.</para>
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<para>The <function>sd_bus_message_append_array_space()</function>
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function appends space for an array of a trivial type to message
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<parameter>m</parameter>. It behaves the same as
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<function>sd_bus_message_append_array()</function>, but instead of
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copying items to the message, it returns a pointer to the
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destination area to the caller in pointer
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<parameter>p</parameter>. The caller should subsequently write the
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array contents to this memory. Modifications to the memory
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pointed to should only occur until the next operation on the bus
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message is invoked. Most importantly, the memory should not be
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altered anymore when another field has been added to the message
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or the message has been sealed.</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 integer. On
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failure, they return a negative errno-style error code.</para>
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</refsect1>
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<xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" />
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<refsect1>
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<title>Notes</title>
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<para><function>sd_bus_append_array()</function> and other
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functions described here are available as a shared library, which
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can be 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_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
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<ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html">The D-Bus specification</ulink>
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</para>
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</refsect1>
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</refentry>
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