153 lines
6.4 KiB
XML
153 lines
6.4 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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This file is part of systemd.
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Copyright 2013 Lennart Poettering
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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_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
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the transaction cookie of a message. The cookie
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uniquely identifies a message within each bus peer,
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but is not globally unique. It is assigned when a
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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
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specified message is a response to. When a reply
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message is generated for a method call message, its
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cookie is copied over into this field. Note that while
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every message that is transferred is identified by a
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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
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parameter and a place to store the 64-bit cookie
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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
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integer. On failure, these calls return a negative
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errno-style error code.</para>
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<para>On success, the cookie/reply cookie is returned
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in the 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><varname>-EINVAL</varname></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><varname>-ENODATA</varname></term>
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<listitem><para>No cookie has been
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assigned to this message. This either
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indicates that the message has not
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been sent yet and hence has no cookie
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assigned, or that the message is not a
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method response message and hence
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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>
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and <function>sd_bus_message_get_reply_cookie()</function>
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interfaces are available as a shared library, which can
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be compiled and linked to with the
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<constant>libsystemd</constant> <citerefentry><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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