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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</span><hr><div class="refentry"><a name="sd_bus_message_append"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_bus_message_append — Attach parts of message based on a format string</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-bus.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int sd_bus_message_append(</code></td><td>sd_bus_message *<var class="pdparam">m</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">types</var>, </td></tr><tr><td> </td><td>...<code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm140498086468192"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p>The <code class="function">sd_bus_message_append</code> function appends
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a sequence of items to message <em class="parameter"><code>m</code></em>. The
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format string <em class="parameter"><code>types</code></em> describes the types of
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arguments that follow.</p><p>The format string is composed of the elements shown in the
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table below. It contains zero or more single "complete types".
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Each complete type may be one of the basic types or a fully
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described container type. A container type may be a structure, a
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variant type code, an array with its element type, or a dictionary
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with its entry type. The format string is
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<code class="constant">NUL</code>-terminated.</p><p>In case of a basic type, one argument of the corresponding
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type is expected.</p><p>A structure is denoted by a sequence of complete types
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between "<code class="literal">(</code>" and "<code class="literal">)</code>". This
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sequence cannot be empty — it must contain at least one type.
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Arguments corresponding to this nested sequence follow the same
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rules as if they were not nested.</p><p>A variant is denoted by "<code class="literal">v</code>". Correspoding
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arguments must include a format string denoting a complete type,
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and following that, arguments corresponding to the specified type.
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</p><p>An array is denoted by "<code class="literal">a</code>" followed by a
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complete type. Corresponding arguments must include the size of
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the array, and then repeated this number of times, arguments
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corresponding to the nested type.</p><p>A dictionary is an array of dictionary entries, denoted by
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"<code class="literal">a</code>" followed by a pair of complete types between
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"<code class="literal">{</code>" and "<code class="literal">}</code>". The first of those
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types must be a basic type. Corresponding arguments must include
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the size of the dictionary, and then repeated this number of
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times, arguments corresponding to each of the two nested
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types.</p><div class="table"><a name="idm140498090358640"></a><p class="title"><b>Table 1. Item format specifiers</b></p><div class="table-contents"><table summary="Item format specifiers" border="1"><colgroup><col><col><col><col></colgroup><thead><tr><th>Specifier</th><th>Constant</th><th>Description</th><th>Size</th></tr></thead><tbody><tr><td>"<code class="literal">y</code>"</td><td><code class="constant">SD_BUS_TYPE_BYTE</code></td><td>unsigned integer</td><td>1 byte</td></tr><tr><td>"<code class="literal">b</code>"</td><td><code class="constant">SD_BUS_TYPE_BOOLEAN</code></td><td>boolean</td><td>4 bytes</td></tr><tr><td>"<code class="literal">n</code>"</td><td><code class="constant">SD_BUS_TYPE_INT16</code></td><td>signed integer</td><td>2 bytes</td></tr><tr><td>"<code class="literal">q</code>"</td><td><code class="constant">SD_BUS_TYPE_UINT16</code></td><td>unsigned integer</td><td>2 bytes</td></tr><tr><td>"<code class="literal">i</code>"</td><td><code class="constant">SD_BUS_TYPE_INT32</code></td><td>signed integer</td><td>4 bytes</td></tr><tr><td>"<code class="literal">u</code>"</td><td><code class="constant">SD_BUS_TYPE_UINT32</code></td><td>unsigned integer</td><td>4 bytes</td></tr><tr><td>"<code class="literal">x</code>"</td><td><code class="constant">SD_BUS_TYPE_INT64</code></td><td>signed integer</td><td>8 bytes</td></tr><tr><td>"<code class="literal">t</code>"</td><td><code class="constant">SD_BUS_TYPE_UINT64</code></td><td>unsigned integer</td><td>8 bytes</td></tr><tr><td>"<code class="literal">d</code>"</td><td><code class="constant">SD_BUS_TYPE_DOUBLE</code></td><td>floating-point</td><td>8 bytes</td></tr><tr><td>"<code class="literal">s</code>"</td><td><code class="constant">SD_BUS_TYPE_STRING</code></td><td>Unicode string</td><td>variable</td></tr><tr><td>"<code class="literal">o</code>"</td><td><code class="constant">SD_BUS_TYPE_OBJECT_PATH</code></td><td>object path</td><td>variable</td></tr><tr><td>"<code class="literal">g</code>"</td><td><code class="constant">SD_BUS_TYPE_SIGNATURE</code></td><td>signature</td><td>variable</td></tr><tr><td>"<code class="literal">h</code>"</td><td><code class="constant">SD_BUS_TYPE_UNIX_FD</code></td><td>UNIX file descriptor</td><td>4 bytes</td></tr><tr><td>"<code class="literal">a</code>"</td><td><code class="constant">SD_BUS_TYPE_ARRAY</code></td><td>array</td><td>determined by array type and size</td></tr><tr><td>"<code class="literal">v</code>"</td><td><code class="constant">SD_BUS_TYPE_VARIANT</code></td><td>variant</td><td>determined by the type argument</td></tr><tr><td>"<code class="literal">(</code>"</td><td><code class="constant">SD_BUS_TYPE_STRUCT_BEGIN</code></td><td>array start</td><td rowspan="2">determined by the nested types</td></tr><tr><td>"<code class="literal">)</code>"</td><td><code class="constant">SD_BUS_TYPE_STRUCT_END</code></td><td>array end</td></tr><tr><td>"<code class="literal">{</code>"</td><td><code class="constant">SD_BUS_TYPE_DICT_ENTRY_BEGIN</code></td><td>dictionary entry start</td><td rowspan="2">determined by the nested types</td></tr><tr><td>"<code class="literal">}</code>"</td><td><code class="constant">SD_BUS_TYPE_DICT_ENTRY_END</code></td><td>dictionary entry end</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1"><a name="idm140498090331984"></a><h2 id="Types string grammar">Types string grammar<a class="headerlink" title="Permalink to this headline" href="#Types%20string%20grammar">¶</a></h2><pre class="programlisting">types ::= complete_type*
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complete_type ::= basic_type | variant | structure | array | dictionary
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basic_type ::= "y" | "n" | "q" | "u" | "i" | "x" | "t" | "d" |
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"b" | "h" |
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"s" | "o" | "g"
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variant ::= "v"
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structure ::= "(" complete_type+ ")"
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array ::= "a" complete_type
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dictionary ::= "a" "{" basic_type complete_type "}"
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</pre></div><div class="refsect1"><a name="idm140498090330160"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples">¶</a></h2><p>Append a single basic type (the string "<code class="literal">a string</code>"):
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</p><pre class="programlisting">sd_bus_message *m;
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...
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sd_bus_message_append(m, "s", "a string");</pre><p>Append all types of integers:</p><pre class="programlisting">uint8_t y = 1;
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int16_t n = 2;
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uint16_t q = 3;
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int32_t i = 4;
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uint32_t u = 5;
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int32_t x = 6;
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uint32_t t = 7;
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double d = 8.0;
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sd_bus_message_append(m, "ynqiuxtd", y, n, q, i, u, x, t, d);</pre><p>Append a structure composed of string and a D-Bus path:</p><pre class="programlisting">sd_bus_message_append(m, "(so)", "a string", "/a/path");
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</pre><p>Append an array of UNIX file descriptors:</p><pre class="programlisting">sd_bus_message_append(m, "ah", 3, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO);
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</pre><p>Append a variant, with the real type "g" (signature),
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and value "sdbusisgood":</p><pre class="programlisting">sd_bus_message_append(m, "v", "g", "sdbusisgood");</pre><p>Append a dictionary containing the mapping {1=>"a", 2=>"b", 3=>""}:
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</p><pre class="programlisting">sd_bus_message_append(m, "a{is}", 3, 1, "a", 2, "b", 3, NULL);
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</pre></div><div class="refsect1"><a name="idm140498090322096"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success, this call returns 0 or a positive
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integer. On failure, this call returns a negative
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errno-style error code.</p></div><div class="refsect1"><a name="errors"></a><h2 id="Errors">Errors<a class="headerlink" title="Permalink to this headline" href="#Errors">¶</a></h2><p>Returned errors may indicate the following problems:</p><div class="variablelist"><dl class="variablelist"><dt id="-EINVAL"><span class="term"><code class="constant">-EINVAL</code></span><a class="headerlink" title="Permalink to this term" href="#-EINVAL">¶</a></dt><dd><p>Specified parameter is invalid.
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</p></dd><dt id="-EPERM"><span class="term"><code class="constant">-EPERM</code></span><a class="headerlink" title="Permalink to this term" href="#-EPERM">¶</a></dt><dd><p>Message has been sealed.
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</p></dd><dt id="-ESTALE"><span class="term"><code class="constant">-ESTALE</code></span><a class="headerlink" title="Permalink to this term" href="#-ESTALE">¶</a></dt><dd><p>Message is in invalid state.
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</p></dd><dt id="-ENXIO"><span class="term"><code class="constant">-ENXIO</code></span><a class="headerlink" title="Permalink to this term" href="#-ENXIO">¶</a></dt><dd><p>Message cannot be appended to.
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</p></dd><dt id="-ENOMEM"><span class="term"><code class="constant">-ENOMEM</code></span><a class="headerlink" title="Permalink to this term" href="#-ENOMEM">¶</a></dt><dd><p>Memory allocation failed.</p></dd></dl></div></div><div class="refsect1"><a name="idm140498090319952"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><code class="function">sd_bus_open_user()</code> and other functions
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described here are available as a shared library, which can be
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compiled and linked to with the
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<code class="constant">libsystemd-bus</code> <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
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file.</p></div><div class="refsect1"><a name="idm140498090316464"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
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<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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<a href="sd-bus.html"><span class="citerefentry"><span class="refentrytitle">sd-bus</span>(3)</span></a>,
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<a href="sd_bus_new.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_new</span>(3)</span></a>,
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<a href="sd_bus_ref.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_ref</span>(3)</span></a>,
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<a href="sd_bus_unref.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_unref</span>(3)</span></a>,
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<a href="ssh.html"><span class="citerefentry"><span class="refentrytitle">ssh</span>(1)</span></a>,
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<a href="systemd-machined.service.html"><span class="citerefentry"><span class="refentrytitle">systemd-machined.service</span>(8)</span></a>,
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<a href="machinectl.html"><span class="citerefentry"><span class="refentrytitle">machinectl</span>(1)</span></a>
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</p></div></div></body></html>
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