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systemd/man/sd_id128_randomize.xml
Lennart Poettering 39d02a175f sd-id128: document everywhere that we treat all UUIDs as Variant 1
So in theory UUID Variant 2 (i.e. microsoft GUIDs) are supposed to be
displayed in native endian. That is of course a bad idea, and Linux
userspace generally didn't implement that, i.e. uuidd and similar.
Hence, let's not bother either, but let's document that we treat
everything the same as Variant 1, even if it declares something else.
2021-06-15 20:58:56 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!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>