<?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 64-bit 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 64-bit 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 a 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>