1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 This file is part of elogind.
7 SPDX-License-Identifier: LGPL-2.1+
10 Copyright 2012 Lennart Poettering
13 <refentry id="sd_id128_to_string">
16 <title>sd_id128_to_string</title>
17 <productname>elogind</productname>
21 <contrib>Developer</contrib>
22 <firstname>Lennart</firstname>
23 <surname>Poettering</surname>
24 <email>lennart@poettering.net</email>
30 <refentrytitle>sd_id128_to_string</refentrytitle>
31 <manvolnum>3</manvolnum>
35 <refname>sd_id128_to_string</refname>
36 <refname>sd_id128_from_string</refname>
37 <refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
42 <funcsynopsisinfo>#include <elogind/sd-id128.h></funcsynopsisinfo>
45 <funcdef>char *<function>sd_id128_to_string</function></funcdef>
46 <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
50 <funcdef>int <function>sd_id128_from_string</function></funcdef>
51 <paramdef>const char *<parameter>s</parameter>, sd_id128_t *<parameter>ret</parameter></paramdef>
58 <title>Description</title>
60 <para><function>sd_id128_to_string()</function> formats a 128-bit
61 ID as a character string. It expects the ID and a string array
62 capable of storing 33 characters. The ID will be formatted as 32
63 lowercase hexadecimal digits and be terminated by a
64 <constant>NUL</constant> byte.</para>
66 <para><function>sd_id128_from_string()</function> implements the reverse operation: it takes a 33 character string
67 with 32 hexadecimal digits (either lowercase or uppercase, terminated by <constant>NUL</constant>) and parses them
68 back into a 128-bit ID returned in <parameter>ret</parameter>. Alternatively, this call can also parse a
69 37-character string with a 128-bit ID formatted as RFC UUID. If <parameter>ret</parameter> is passed as NULL the
70 function will validate the passed ID string, but not actually return it in parsed form.</para>
72 <para>For more information about the <literal>sd_id128_t</literal>
74 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
75 Note that these calls operate the same way on all architectures,
76 i.e. the results do not depend on endianness.</para>
78 <para>When formatting a 128-bit ID into a string, it is often
79 easier to use a format string for
80 <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
81 This is easily done using the
82 <function>SD_ID128_FORMAT_STR</function> and
83 <function>SD_ID128_FORMAT_VAL()</function> macros. For more
85 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
89 <title>Return Value</title>
91 <para><function>sd_id128_to_string()</function> always succeeds
92 and returns a pointer to the string array passed in.
93 <function>sd_id128_from_string</function> returns 0 on success, in
94 which case <parameter>ret</parameter> is filled in, or a negative
95 errno-style error code.</para>
101 <para>The <function>sd_id128_to_string()</function> and
102 <function>sd_id128_from_string()</function> interfaces are
103 available as a shared library, which can be compiled and linked to
105 <literal>libelogind</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
110 <title>See Also</title>
113 <!-- 0 /// elogind is in section 8
114 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
116 <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
118 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
119 <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>