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This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
183 lines
7.5 KiB
XML
183 lines
7.5 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_bus_send"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_send</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_send</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_send</refname>
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<refname>sd_bus_send_to</refname>
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<refname>sd_bus_message_send</refname>
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<refpurpose>Queue a D-Bus message for transfer</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_send</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>sd_bus_message *<parameter>m</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_send_to</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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<paramdef>const char *<parameter>destination</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 sd_bus_message_send</funcdef>
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<paramdef>sd_bus_message *<parameter>m</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_send()</function> queues the bus message object <parameter>m</parameter> for
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transfer. If <parameter>bus</parameter> is <constant>NULL</constant>, the bus that
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<parameter>m</parameter> is attached to is used. <parameter>bus</parameter> only needs to be set when the
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message is sent to a different bus than the one it's attached to, for example when forwarding messages.
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If the output parameter <parameter>cookie</parameter> is not <constant>NULL</constant>, it is set to the
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message identifier. This value can later be used to match incoming replies to their corresponding
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messages. If <parameter>cookie</parameter> is set to <constant>NULL</constant> and the message is not
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sealed, <function>sd_bus_send()</function> assumes the message <parameter>m</parameter> doesn't expect a
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reply and adds the necessary headers to indicate this.</para>
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<para>Note that in most scenarios, <function>sd_bus_send()</function> should not be called
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directly. Instead, use higher level functions such as
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<citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
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<citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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which call <function>sd_bus_send()</function> internally.</para>
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<para><function>sd_bus_send_to()</function> is a shorthand for sending a message to a specific
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destination. It's main use case is to simplify sending unicast signal messages (signals that only have a
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single receiver). It's behavior is similar to calling
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<citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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followed by calling <function>sd_bus_send()</function>.</para>
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<para><function>sd_bus_send()</function>/<function>sd_bus_send_to()</function> will write the message
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directly to the underlying transport (e.g. kernel socket buffer) if possible. If the connection is not
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set up fully yet the message is queued locally. If the transport buffers are congested any unwritten
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message data is queued locally, too. If the connection has been closed or is currently being closed the
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call fails.
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<citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry> should
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be invoked to write out any queued message data to the transport.</para>
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<para><function>sd_bus_message_send()</function> is the same as <function>sd_bus_send()</function> but
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without the first and last argument. <function>sd_bus_message_send(m)</function> is equivalent to
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<function>sd_bus_send(sd_bus_message_get_bus(m), m, NULL)</function>.</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 functions return a non-negative integer. On failure, they return a negative
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errno-style error code.</para>
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<refsect2 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>The input parameter <parameter>m</parameter> is <constant>NULL</constant>.
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</para>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EOPNOTSUPP</constant></term>
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<listitem><para>The bus connection does not support sending file descriptors.
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</para>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The bus connection was allocated in a parent process and is being reused in a child
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process after <function>fork()</function>.</para>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOBUFS</constant></term>
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<listitem><para>The bus connection's write queue is full.</para>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOTCONN</constant></term>
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<listitem><para>The input parameter <parameter>bus</parameter> is
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<constant>NULL</constant> or the bus is not connected.</para>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECONNRESET</constant></term>
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<listitem><para>The bus connection was closed while waiting for the response.
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</para>
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<xi:include href="version-info.xml" xpointer="v246"/></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>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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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_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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