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https://github.com/systemd/systemd-stable.git
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298 lines
9.7 KiB
XML
298 lines
9.7 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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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_message_append_basic">
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<refentryinfo>
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<title>sd_bus_message_append_basic</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_basic</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_basic</refname>
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<refpurpose>Attach a single field to a 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_basic</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 void *<parameter>p</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_message_append_basic()</function> appends a
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single field to the message <parameter>m</parameter>. The
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parameter <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 basic types as
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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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the table below.
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</para>
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<table id='format-specifiers'>
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<title>Item type specifiers</title>
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<tgroup cols='5'>
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<colspec colname='specifier' />
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<colspec colname='constant' />
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<colspec colname='description' />
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<colspec colname='size' />
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<colspec colname='ctype' />
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<thead>
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<row>
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<entry>Specifier</entry>
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<entry>Constant</entry>
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<entry>Description</entry>
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<entry>Size</entry>
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<entry>Expected C Type</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><literal>y</literal></entry>
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<entry><constant>SD_BUS_TYPE_BYTE</constant></entry>
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<entry>unsigned integer</entry>
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<entry>1 byte</entry>
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<entry>uint8_t</entry>
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</row>
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<row>
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<entry><literal>b</literal></entry>
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<entry><constant>SD_BUS_TYPE_BOOLEAN</constant></entry>
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<entry>boolean</entry>
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<entry>4 bytes</entry>
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<entry>int</entry>
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</row>
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<row>
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<entry><literal>n</literal></entry>
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<entry><constant>SD_BUS_TYPE_INT16</constant></entry>
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<entry>signed integer</entry>
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<entry>2 bytes</entry>
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<entry>int16_t</entry>
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</row>
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<row>
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<entry><literal>q</literal></entry>
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<entry><constant>SD_BUS_TYPE_UINT16</constant></entry>
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<entry>unsigned integer</entry>
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<entry>2 bytes</entry>
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<entry>uint16_t</entry>
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</row>
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<row>
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<entry><literal>i</literal></entry>
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<entry><constant>SD_BUS_TYPE_INT32</constant></entry>
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<entry>signed integer</entry>
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<entry>4 bytes</entry>
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<entry>int32_t</entry>
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</row>
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<row>
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<entry><literal>u</literal></entry>
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<entry><constant>SD_BUS_TYPE_UINT32</constant></entry>
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<entry>unsigned integer</entry>
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<entry>4 bytes</entry>
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<entry>uint32_t</entry>
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</row>
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<row>
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<entry><literal>x</literal></entry>
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<entry><constant>SD_BUS_TYPE_INT64</constant></entry>
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<entry>signed integer</entry>
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<entry>8 bytes</entry>
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<entry>int64_t</entry>
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</row>
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<row>
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<entry><literal>t</literal></entry>
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<entry><constant>SD_BUS_TYPE_UINT64</constant></entry>
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<entry>unsigned integer</entry>
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<entry>8 bytes</entry>
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<entry>uint64_t</entry>
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</row>
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<row>
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<entry><literal>d</literal></entry>
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<entry><constant>SD_BUS_TYPE_DOUBLE</constant></entry>
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<entry>floating-point</entry>
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<entry>8 bytes</entry>
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<entry>double</entry>
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</row>
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<row>
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<entry><literal>s</literal></entry>
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<entry><constant>SD_BUS_TYPE_STRING</constant></entry>
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<entry>Unicode string</entry>
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<entry>variable</entry>
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<entry>char[]</entry>
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</row>
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<row>
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<entry><literal>o</literal></entry>
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<entry><constant>SD_BUS_TYPE_OBJECT_PATH</constant></entry>
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<entry>object path</entry>
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<entry>variable</entry>
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<entry>char[]</entry>
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</row>
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<row>
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<entry><literal>g</literal></entry>
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<entry><constant>SD_BUS_TYPE_SIGNATURE</constant></entry>
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<entry>signature</entry>
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<entry>variable</entry>
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<entry>char[]</entry>
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</row>
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<row>
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<entry><literal>h</literal></entry>
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<entry><constant>SD_BUS_TYPE_UNIX_FD</constant></entry>
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<entry>UNIX file descriptor</entry>
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<entry>4 bytes</entry>
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<entry>int</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>The value of the parameter is copied into a memory area held
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by the message object, stays in the possession of the caller and
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may hence be freely changed after this call without affecting the
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bus message it has been added to. If <parameter>type</parameter>
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is <literal>h</literal> (UNIX file descriptor), the descriptor is
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duplicated by this call and the passed descriptor stays in
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possession of the caller.</para>
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<para>For types <literal>s</literal>, <literal>o</literal>, and
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<literal>g</literal>, the parameter <parameter>p</parameter> is
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interpreted as a pointer to a <constant>NUL</constant>-terminated
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character sequence. As a special case, a <constant>NULL</constant>
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pointer is interpreted as an empty string. The string should be
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valid Unicode string encoded as UTF-8. In case of the two latter
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types, the additional requirements for a D-Bus object path or
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type signature should be satisfied. Those requirements should be
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verified by the recipient of the message.
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</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, this call returns 0 or a positive integer. On
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failure, it returns a negative errno-style error code.</para>
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</refsect1>
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<refsect1 id='errors'>
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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>-EINVAL</constant></term>
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<listitem><para>Specified parameter is invalid.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EPERM</constant></term>
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<listitem><para>Message has been sealed.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ESTALE</constant></term>
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<listitem><para>Message is in invalid state.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENXIO</constant></term>
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<listitem><para>Message cannot be appended to.
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</para></listitem>
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</varlistentry>
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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>The <function>sd_bus_append_basic()</function> function
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described here is 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_message_append</refentrytitle><manvolnum>3</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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