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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_id128_get_machine"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_id128_get_machine, sd_id128_get_boot — Retrieve 128-bit IDs</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-id128.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_id128_get_machine</b>(</code></td><td>sd_id128_t *<var class="pdparam">ret</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_id128_get_boot</b>(</code></td><td>sd_id128_t *<var class="pdparam">ret</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm140317247803792"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_id128_get_machine()</code> returns the
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machine ID of the executing host. This reads and parses the
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<a href="machine-id.html"><span class="citerefentry"><span class="refentrytitle">machine-id</span>(5)</span></a>
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file. This function caches the machine ID internally to make
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retrieving the machine ID a cheap operation.</p><p><code class="function">sd_id128_get_boot()</code> returns the boot ID
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of the executing kernel. This reads and parses the
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<code class="filename">/proc/sys/kernel/random/boot_id</code> file exposed
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by the kernel. It is randomly generated early at boot and is
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unique for every running kernel instance. See
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<a href="http://man7.org/linux/man-pages/man4/random.4.html"><span class="citerefentry"><span class="refentrytitle">random</span>(4)</span></a>
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for more information. This function also internally caches the
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returned ID to make this call a cheap operation.</p><p>Note that <code class="function">sd_id128_get_boot()</code> always
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returns a UUID v4 compatible ID.
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<code class="function">sd_id128_get_machine()</code> will also return a
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UUID v4-compatible ID on new installations but might not on older.
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It is possible to convert the machine ID into a UUID v4-compatible
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one. For more information, see
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<a href="machine-id.html"><span class="citerefentry"><span class="refentrytitle">machine-id</span>(5)</span></a>.</p><p>For more information about the "<code class="literal">sd_id128_t</code>"
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type see
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<a href="sd-id128.html"><span class="citerefentry"><span class="refentrytitle">sd-id128</span>(3)</span></a>.</p></div><div class="refsect1"><a name="idm140317244009808"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>The two calls return 0 on success (in which case
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<em class="parameter"><code>ret</code></em> is filled in), or a negative
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errno-style error code.</p></div><div class="refsect1"><a name="idm140317244007968"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The <code class="function">sd_id128_get_machine()</code> and
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<code class="function">sd_id128_get_boot()</code> interfaces are available
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as a shared library, which can be compiled and linked to with the
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"<code class="literal">libsystemd</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="idm140317244003408"></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-id128.html"><span class="citerefentry"><span class="refentrytitle">sd-id128</span>(3)</span></a>,
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<a href="machine-id.html"><span class="citerefentry"><span class="refentrytitle">machine-id</span>(5)</span></a>,
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<a href="http://man7.org/linux/man-pages/man4/random.4.html"><span class="citerefentry"><span class="refentrytitle">random</span>(4)</span></a>,
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<a href="sd_id128_randomize.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_randomize</span>(3)</span></a>
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</p></div></div></body></html>
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