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systemd/man/sd_id128_to_string.xml
Zbigniew Jędrzejewski-Szmek 11a1589223 tree-wide: drop license boilerplate
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.

I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
2018-04-06 18:58:55 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
This file is part of systemd.
Copyright 2012 Lennart Poettering
-->
<refentry id="sd_id128_to_string">
<refentryinfo>
<title>sd_id128_to_string</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_id128_to_string</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_id128_to_string</refname>
<refname>sd_id128_from_string</refname>
<refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>char *<function>sd_id128_to_string</function></funcdef>
<paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_id128_from_string</function></funcdef>
<paramdef>const char *<parameter>s</parameter>, sd_id128_t *<parameter>ret</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_id128_to_string()</function> formats a 128-bit
ID as a character string. It expects the ID and a string array
capable of storing 33 characters. The ID will be formatted as 32
lowercase hexadecimal digits and be terminated by a
<constant>NUL</constant> byte.</para>
<para><function>sd_id128_from_string()</function> implements the reverse operation: it takes a 33 character string
with 32 hexadecimal digits (either lowercase or uppercase, terminated by <constant>NUL</constant>) and parses them
back into a 128-bit ID returned in <parameter>ret</parameter>. Alternatively, this call can also parse a
37-character string with a 128-bit ID formatted as RFC UUID. If <parameter>ret</parameter> is passed as NULL the
function will validate the passed ID string, but not actually return it in parsed form.</para>
<para>For more information about the <literal>sd_id128_t</literal>
type see
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
Note that these calls operate the same way on all architectures,
i.e. the results do not depend on endianness.</para>
<para>When formatting a 128-bit ID into a string, it is often
easier to use a format string for
<citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
This is easily done using the
<function>SD_ID128_FORMAT_STR</function> and
<function>SD_ID128_FORMAT_VAL()</function> macros. For more
information see
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para><function>sd_id128_to_string()</function> always succeeds
and returns a pointer to the string array passed in.
<function>sd_id128_from_string</function> returns 0 on success, in
which case <parameter>ret</parameter> is filled in, or a negative
errno-style error code.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_id128_to_string()</function> and
<function>sd_id128_from_string()</function> interfaces are
available as a shared library, which can be compiled and linked to
with the
<literal>libsystemd</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>