man/sd_id128_get_machine.html


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53

<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_id128_get_machine</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
    a.headerlink {
      color: #c60f0f;
      font-size: 0.8em;
      padding: 0 4px 0 4px;
      text-decoration: none;
      visibility: hidden;
    }

    a.headerlink:hover {
      background-color: #c60f0f;
      color: white;
    }

    h1:hover > a.headerlink, h2:hover > a.headerlink, h3:hover > a.headerlink, dt:hover > a.headerlink {
      visibility: visible;
    }
  </style><a href="index.html">Index </a>·
  <a href="systemd.directives.html">Directives </a>·
  <a href="../python-systemd/index.html">Python </a>·

  <span style="float:right">systemd 221</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 &lt;systemd/sd-id128.h&gt;</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="idm47885800841280"></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
    machine ID of the executing host. This reads and parses the
    <a href="machine-id.html"><span class="citerefentry"><span class="refentrytitle">machine-id</span>(5)</span></a>
    file. This function caches the machine ID internally to make
    retrieving the machine ID a cheap operation.</p><p><code class="function">sd_id128_get_boot()</code> returns the boot ID
    of the executing kernel. This reads and parses the
    <code class="filename">/proc/sys/kernel/random/boot_id</code> file exposed
    by the kernel. It is randomly generated early at boot and is
    unique for every running kernel instance. See
    <a href="http://man7.org/linux/man-pages/man4/random.4.html"><span class="citerefentry"><span class="refentrytitle">random</span>(4)</span></a>
    for more information. This function also internally caches the
    returned ID to make this call a cheap operation.</p><p>Note that <code class="function">sd_id128_get_boot()</code> always
    returns a UUID v4 compatible ID.
    <code class="function">sd_id128_get_machine()</code> will also return a
    UUID v4-compatible ID on new installations but might not on older.
    It is possible to convert the machine ID into a UUID v4-compatible
    one. For more information, see
    <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>"
    type see
    <a href="sd-id128.html"><span class="citerefentry"><span class="refentrytitle">sd-id128</span>(3)</span></a>.</p></div><div class="refsect1"><a name="idm47885800831536"></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
    <em class="parameter"><code>ret</code></em> is filled in), or a negative
    errno-style error code.</p></div><div class="refsect1"><a name="idm47885800829760"></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
    <code class="function">sd_id128_get_boot()</code> interfaces are available
    as a shared library, which can be compiled and linked to with the
    "<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>
    file.</p></div><div class="refsect1"><a name="idm47885800825616"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
      <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
      <a href="sd-id128.html"><span class="citerefentry"><span class="refentrytitle">sd-id128</span>(3)</span></a>,
      <a href="machine-id.html"><span class="citerefentry"><span class="refentrytitle">machine-id</span>(5)</span></a>,
      <a href="http://man7.org/linux/man-pages/man4/random.4.html"><span class="citerefentry"><span class="refentrytitle">random</span>(4)</span></a>,
      <a href="sd_id128_randomize.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_randomize</span>(3)</span></a>
    </p></div></div></body></html>