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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_bus_message_get_cookie">
<refentryinfo>
<title>sd_bus_message_get_cookie</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_message_get_cookie</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_message_get_cookie</refname>
<refname>sd_bus_message_get_reply_cookie</refname>
<refpurpose>Returns the transaction cookie of a message</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_message_get_cookie</function></funcdef>
<paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
<paramdef>uint64_t* <parameter>cookie</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_message_get_reply_cookie</function></funcdef>
<paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
<paramdef>uint64_t* <parameter>cookie</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_message_get_cookie()</function> returns
the transaction cookie of a message. The cookie
uniquely identifies a message within each bus peer,
but is not globally unique. It is assigned when a
message is sent.</para>
<para><function>sd_bus_message_get_reply_cookie()</function>
returns the transaction cookie of the message the
specified message is a response to. When a reply
message is generated for a method call message, its
cookie is copied over into this field. Note that while
every message that is transferred is identified by a
cookie, only response messages carry a reply cookie
field.</para>
<para>Both functions take a message object as first
parameter and a place to store the 64bit cookie
in.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these calls return 0 or a positive
integer. On failure, these calls return a negative
errno-style error code.</para>
<para>On success, the cookie/reply cookie is returned
in the specified 64bit unsigned integer variable.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><varname>-EINVAL</varname></term>
<listitem><para>A specified parameter
is invalid.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>-ENODATA</varname></term>
<listitem><para>No cookie has been
assigned to this message. This either
indicates that the message has not
been sent yet and hence has no cookie
assigned, or that the message is not a
method response message and hence
carries to reply cookie
field.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_bus_message_get_cookie()</function>
and <function>sd_bus_message_get_reply_cookie()</function>
interfaces are available as a shared library, which can
be compiled and linked to with the
<constant>libsystemd-bus</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</refsect1>
<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_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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