man/sd_bus_message_append.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
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   8 Copyright 2014 Zbigniew Jędrzejewski-Szmek
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  11 under the terms of the GNU Lesser General Public License as published by
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  23
  24 <refentry id="sd_bus_message_append" conditional="ENABLE_KDBUS"
  25           xmlns:xi="http://www.w3.org/2001/XInclude">
  26
  27   <refentryinfo>
  28     <title>sd_bus_message_append</title>
  29     <productname>systemd</productname>
  30
  31     <authorgroup>
  32       <author>
  33         <contrib>A monkey with a typewriter</contrib>
  34         <firstname>Zbigniew</firstname>
  35         <surname>Jędrzejewski-Szmek</surname>
  36         <email>zbyszek@in.waw.pl</email>
  37       </author>
  38     </authorgroup>
  39   </refentryinfo>
  40
  41   <refmeta>
  42     <refentrytitle>sd_bus_message_append</refentrytitle>
  43     <manvolnum>3</manvolnum>
  44   </refmeta>
  45
  46   <refnamediv>
  47     <refname>sd_bus_message_append</refname>
  48
  49     <refpurpose>Attach parts of message based on a format string</refpurpose>
  50   </refnamediv>
  51
  52   <refsynopsisdiv>
  53     <funcsynopsis>
  54       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  55
  56       <funcprototype>
  57         <funcdef>int sd_bus_message_append</funcdef>
  58         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  59         <paramdef>const char *<parameter>types</parameter></paramdef>
  60         <paramdef>...</paramdef>
  61       </funcprototype>
  62     </funcsynopsis>
  63   </refsynopsisdiv>
  64
  65   <refsect1>
  66     <title>Description</title>
  67
  68     <para>The <function>sd_bus_message_append</function> function appends
  69     a sequence of items to message <parameter>m</parameter>. The
  70     format string <parameter>types</parameter> describes the types of
  71     arguments that follow.</para>
  72
  73     <para>The format string is composed of the elements shown in the
  74     table below. It contains zero or more single "complete types".
  75     Each complete type may be one of the basic types or a fully
  76     described container type. A container type may be a structure, a
  77     variant type code, an array with its element type, or a dictionary
  78     with its entry type. The format string is
  79     <constant>NUL</constant>-terminated.</para>
  80
  81     <para>In case of a basic type, one argument of the corresponding
  82     type is expected.</para>
  83
  84     <para>A structure is denoted by a sequence of complete types
  85     between <literal>(</literal> and <literal>)</literal>. This
  86     sequence cannot be empty — it must contain at least one type.
  87     Arguments corresponding to this nested sequence follow the same
  88     rules as if they were not nested.</para>
  89
  90     <para>A variant is denoted by <literal>v</literal>. Correspoding
  91     arguments must include a format string denoting a complete type,
  92     and following that, arguments corresponding to the specified type.
  93     </para>
  94
  95     <para>An array is denoted by <literal>a</literal> followed by a
  96     complete type. Corresponding arguments must include the size of
  97     the array, and then repeated this number of times, arguments
  98     corresponding to the nested type.</para>
  99
 100     <para>A dictionary is an array of dictionary entries, denoted by
 101     <literal>a</literal> followed by a pair of complete types between
 102     <literal>{</literal> and <literal>}</literal>. The first of those
 103     types must be a basic type. Corresponding arguments must include
 104     the size of the dictionary, and then repeated this number of
 105     times, arguments corresponding to each of the two nested
 106     types.</para>
 107
 108     <table>
 109       <title>Item format specifiers</title>
 110
 111       <tgroup cols='4'>
 112         <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers'])//colspec" />
 113         <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//thead)" />
 114
 115         <tbody>
 116           <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//tbody/*)" />
 117
 118           <row>
 119             <entry><literal>a</literal></entry>
 120             <entry><constant>SD_BUS_TYPE_ARRAY</constant></entry>
 121             <entry>array</entry>
 122             <entry>determined by array type and size</entry>
 123           </row>
 124
 125           <row>
 126             <entry><literal>v</literal></entry>
 127             <entry><constant>SD_BUS_TYPE_VARIANT</constant></entry>
 128             <entry>variant</entry>
 129             <entry>determined by the type argument</entry>
 130           </row>
 131
 132           <row>
 133             <entry><literal>(</literal></entry>
 134             <entry><constant>SD_BUS_TYPE_STRUCT_BEGIN</constant></entry>
 135             <entry>array start</entry>
 136             <entry morerows="1">determined by the nested types</entry>
 137           </row>
 138           <row>
 139             <entry><literal>)</literal></entry>
 140             <entry><constant>SD_BUS_TYPE_STRUCT_END</constant></entry>
 141             <entry>array end</entry>
 142           </row>
 143
 144           <row>
 145             <entry><literal>{</literal></entry>
 146             <entry><constant>SD_BUS_TYPE_DICT_ENTRY_BEGIN</constant></entry>
 147             <entry>dictionary entry start</entry>
 148             <entry morerows="1">determined by the nested types</entry>
 149           </row>
 150           <row>
 151             <entry><literal>}</literal></entry>
 152             <entry><constant>SD_BUS_TYPE_DICT_ENTRY_END</constant></entry>
 153             <entry>dictionary entry end</entry>
 154           </row>
 155        </tbody>
 156       </tgroup>
 157     </table>
 158   </refsect1>
 159
 160   <refsect1>
 161     <title>Types string grammar</title>
 162
 163     <programlisting>types ::= complete_type*
 164 complete_type ::= basic_type | variant | structure | array | dictionary
 165 basic_type ::= "y" | "n" | "q" | "u" | "i" | "x" | "t" | "d" |
 166                "b" | "h" |
 167                "s" | "o" | "g"
 168 variant ::= "v"
 169 structure ::= "(" complete_type+ ")"
 170 array ::= "a" complete_type
 171 dictionary ::= "a" "{" basic_type complete_type "}"
 172 </programlisting>
 173   </refsect1>
 174
 175   <refsect1>
 176     <title>Examples</title>
 177
 178     <para>Append a single basic type (the string <literal>a string</literal>):
 179     </para>
 180
 181     <programlisting>sd_bus_message *m;
 182 ...
 183 sd_bus_message_append(m, "s", "a string");</programlisting>
 184
 185     <para>Append all types of integers:</para>
 186
 187     <programlisting>uint8_t y = 1;
 188 int16_t n = 2;
 189 uint16_t q = 3;
 190 int32_t i = 4;
 191 uint32_t u = 5;
 192 int32_t x = 6;
 193 uint32_t t = 7;
 194 double d = 8.0;
 195 sd_bus_message_append(m, "ynqiuxtd", y, n, q, i, u, x, t, d);</programlisting>
 196
 197      <para>Append a structure composed of string and a D-Bus path:</para>
 198
 199      <programlisting>sd_bus_message_append(m, "(so)", "a string", "/a/path");
 200 </programlisting>
 201
 202      <para>Append an array of UNIX file descriptors:</para>
 203
 204      <programlisting>sd_bus_message_append(m, "ah", 3, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO);
 205 </programlisting>
 206
 207      <para>Append a variant, with the real type "g" (signature),
 208      and value "sdbusisgood":</para>
 209
 210      <programlisting>sd_bus_message_append(m, "v", "g", "sdbusisgood");</programlisting>
 211
 212      <para>Append a dictionary containing the mapping {1=>"a", 2=>"b", 3=>""}:
 213      </para>
 214
 215      <programlisting>sd_bus_message_append(m, "a{is}", 3, 1, "a", 2, "b", 3, NULL);
 216      </programlisting>
 217   </refsect1>
 218
 219   <refsect1>
 220     <title>Return Value</title>
 221
 222     <para>On success, this call returns 0 or a positive
 223     integer. On failure, this call returns a negative
 224     errno-style error code.</para>
 225   </refsect1>
 226
 227   <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" />
 228
 229   <refsect1>
 230     <title>Notes</title>
 231
 232     <para><function>sd_bus_open_user()</function> and other functions
 233     described here are available as a shared library, which can be
 234     compiled and linked to with the
 235     <constant>libsystemd-bus</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 236     file.</para>
 237   </refsect1>
 238
 239   <refsect1>
 240     <title>See Also</title>
 241
 242     <para>
 243       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 244       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 245       <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 246       <citerefentry><refentrytitle>sd_bus_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 247       <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 248       <citerefentry><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 249       <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 250       <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 251     </para>
 252   </refsect1>
 253
 254 </refentry>