<?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 2014 Zbigniew Jędrzejewski-Szmek 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_append" conditional="ENABLE_KDBUS" xmlns:xi="http://www.w3.org/2001/XInclude"> <refentryinfo> <title>sd_bus_message_append</title> <productname>systemd</productname> <authorgroup> <author> <contrib>A monkey with a typewriter</contrib> <firstname>Zbigniew</firstname> <surname>Jędrzejewski-Szmek</surname> <email>zbyszek@in.waw.pl</email> </author> </authorgroup> </refentryinfo> <refmeta> <refentrytitle>sd_bus_message_append</refentrytitle> <manvolnum>3</manvolnum> </refmeta> <refnamediv> <refname>sd_bus_message_append</refname> <refpurpose>Attach parts of message based on a format string</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> <funcprototype> <funcdef>int sd_bus_message_append</funcdef> <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> <paramdef>const char *<parameter>types</parameter></paramdef> <paramdef>...</paramdef> </funcprototype> </funcsynopsis> </refsynopsisdiv> <refsect1> <title>Description</title> <para>The <function>sd_bus_message_append</function> function appends a sequence of items to message <parameter>m</parameter>. The format string <parameter>types</parameter> describes the types of arguments that follow.</para> <para>The format string is composed of the elements shown in the table below. It contains zero or more single "complete types". Each complete type may be one of the basic types or a fully described container type. A container type may be a structure, a variant type code, an array with its element type, or a dictionary with its entry type. The format string is <constant>NUL</constant>-terminated.</para> <para>In case of a basic type, one argument of the corresponding type is expected.</para> <para>A structure is denoted by a sequence of complete types between <literal>(</literal> and <literal>)</literal>. This sequence cannot be empty — it must contain at least one type. Arguments corresponding to this nested sequence follow the same rules as if they were not nested.</para> <para>A variant is denoted by <literal>v</literal>. Correspoding arguments must include a format string denoting a complete type, and following that, arguments corresponding to the specified type. </para> <para>An array is denoted by <literal>a</literal> followed by a complete type. Corresponding arguments must include the size of the array, and then repeated this number of times, arguments corresponding to the nested type.</para> <para>A dictionary is an array of dictionary entries, denoted by <literal>a</literal> followed by a pair of complete types between <literal>{</literal> and <literal>}</literal>. The first of those types must be a basic type. Corresponding arguments must include the size of the dictionary, and then repeated this number of times, arguments corresponding to each of the two nested types.</para> <table> <title>Item format specifiers</title> <tgroup cols='4'> <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers'])//colspec" /> <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//thead)" /> <tbody> <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//tbody/*)" /> <row> <entry><literal>a</literal></entry> <entry><constant>SD_BUS_TYPE_ARRAY</constant></entry> <entry>array</entry> <entry>determined by array type and size</entry> </row> <row> <entry><literal>v</literal></entry> <entry><constant>SD_BUS_TYPE_VARIANT</constant></entry> <entry>variant</entry> <entry>determined by the type argument</entry> </row> <row> <entry><literal>(</literal></entry> <entry><constant>SD_BUS_TYPE_STRUCT_BEGIN</constant></entry> <entry>array start</entry> <entry morerows="1">determined by the nested types</entry> </row> <row> <entry><literal>)</literal></entry> <entry><constant>SD_BUS_TYPE_STRUCT_END</constant></entry> <entry>array end</entry> </row> <row> <entry><literal>{</literal></entry> <entry><constant>SD_BUS_TYPE_DICT_ENTRY_BEGIN</constant></entry> <entry>dictionary entry start</entry> <entry morerows="1">determined by the nested types</entry> </row> <row> <entry><literal>}</literal></entry> <entry><constant>SD_BUS_TYPE_DICT_ENTRY_END</constant></entry> <entry>dictionary entry end</entry> </row> </tbody> </tgroup> </table> </refsect1> <refsect1> <title>Types string grammar</title> <programlisting>types ::= complete_type* complete_type ::= basic_type | variant | structure | array | dictionary basic_type ::= "y" | "n" | "q" | "u" | "i" | "x" | "t" | "d" | "b" | "h" | "s" | "o" | "g" variant ::= "v" structure ::= "(" complete_type+ ")" array ::= "a" complete_type dictionary ::= "a" "{" basic_type complete_type "}" </programlisting> </refsect1> <refsect1> <title>Examples</title> <para>Append a single basic type (the string <literal>a string</literal>): </para> <programlisting>sd_bus_message *m; ... sd_bus_message_append(m, "s", "a string");</programlisting> <para>Append all types of integers:</para> <programlisting>uint8_t y = 1; int16_t n = 2; uint16_t q = 3; int32_t i = 4; uint32_t u = 5; int32_t x = 6; uint32_t t = 7; double d = 8.0; sd_bus_message_append(m, "ynqiuxtd", y, n, q, i, u, x, t, d);</programlisting> <para>Append a structure composed of string and a D-Bus path:</para> <programlisting>sd_bus_message_append(m, "(so)", "a string", "/a/path"); </programlisting> <para>Append an array of UNIX file descriptors:</para> <programlisting>sd_bus_message_append(m, "ah", 3, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO); </programlisting> <para>Append a variant, with the real type "g" (signature), and value "sdbusisgood":</para> <programlisting>sd_bus_message_append(m, "v", "g", "sdbusisgood");</programlisting> <para>Append a dictionary containing the mapping {1=>"a", 2=>"b", 3=>""}: </para> <programlisting>sd_bus_message_append(m, "a{is}", 3, 1, "a", 2, "b", 3, NULL); </programlisting> </refsect1> <refsect1> <title>Return Value</title> <para>On success, this call returns 0 or a positive integer. On failure, this call returns a negative errno-style error code.</para> </refsect1> <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" /> <refsect1> <title>Notes</title> <para><function>sd_bus_open_user()</function> and other functions described here 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>, <citerefentry><refentrytitle>sd_bus_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> </para> </refsect1> </refentry>