136 lines
4.4 KiB
XML
136 lines
4.4 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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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2013 Lennart Poettering
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-->
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<refentry id="sd_bus_message_get_cookie">
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<refentryinfo>
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<title>sd_bus_message_get_cookie</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</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_get_cookie</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_get_cookie</refname>
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<refname>sd_bus_message_get_reply_cookie</refname>
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<refpurpose>Returns the transaction cookie of 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 <function>sd_bus_message_get_cookie</function></funcdef>
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<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
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<paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_message_get_reply_cookie</function></funcdef>
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<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
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<paramdef>uint64_t *<parameter>cookie</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_get_cookie()</function> returns the
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transaction cookie of a message. The cookie uniquely identifies a
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message within each bus peer, but is not globally unique. It is
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assigned when a message is sent.</para>
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<para><function>sd_bus_message_get_reply_cookie()</function>
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returns the transaction cookie of the message the specified
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message is a response to. When a reply message is generated for a
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method call message, its cookie is copied over into this field.
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Note that while every message that is transferred is identified by
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a cookie, only response messages carry a reply cookie
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field.</para>
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<para>Both functions take a message object as first parameter and
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a place to store the 64-bit cookie in.</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, these calls return a negative errno-style error
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code.</para>
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<para>On success, the cookie/reply cookie is returned in the
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specified 64-bit unsigned integer variable.</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><constant>-EINVAL</constant></term>
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<listitem><para>A specified parameter
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is invalid.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENODATA</constant></term>
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<listitem><para>No cookie has been assigned to this message.
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This either indicates that the message has not been sent yet
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and hence has no cookie assigned, or that the message is not a
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method response message and hence carries a reply cookie
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field.</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_message_get_cookie()</function> and
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<function>sd_bus_message_get_reply_cookie()</function> interfaces
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are available as a shared library, which can be compiled and
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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_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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