systemd/man/sd_id128_randomize.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

<refentry id="sd_id128_randomize" xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_id128_randomize</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_id128_randomize</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_id128_randomize</refname>
    <refpurpose>Generate 128-bit IDs</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_id128_randomize</function></funcdef>
        <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_id128_randomize()</function> generates a new
    randomized 128-bit ID and returns it in
    <parameter>ret</parameter>. Every invocation returns a new
    randomly generated ID. This uses the
    <filename>/dev/urandom</filename> kernel random number
    generator.</para>

    <para>Note that <function>sd_id128_randomize()</function> always returns a UUID Variant 1 Version 4
    compatible ID. It is hence guaranteed that this function will never return the ID consisting of all zero
    or all one bits (<constant>SD_ID128_NULL</constant>, <constant>SD_ID128_ALLF</constant>).</para>

    <para>For more information about the <literal>sd_id128_t</literal>
    type, see
    <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

    <para><citerefentry><refentrytitle>systemd-id128</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
    <command>new</command> command may be used as a command line front-end for
    <function>sd_id128_randomize()</function>.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>The call returns 0 on success (in which case
    <parameter>ret</parameter> is filled in), or a negative
    errno-style error code.</para>
  </refsect1>

  <xi:include href="libsystemd-pkgconfig.xml" />

  <refsect1>
    <title>See Also</title>

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_id128_get_machine</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>