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 SPDX-License-Identifier: LGPL-2.1+
9 <refentry id="sd_id128_to_string" xmlns:xi="http://www.w3.org/2001/XInclude">
12 <title>sd_id128_to_string</title>
13 <productname>elogind</productname>
17 <contrib>Developer</contrib>
18 <firstname>Lennart</firstname>
19 <surname>Poettering</surname>
20 <email>lennart@poettering.net</email>
26 <refentrytitle>sd_id128_to_string</refentrytitle>
27 <manvolnum>3</manvolnum>
31 <refname>sd_id128_to_string</refname>
32 <refname>sd_id128_from_string</refname>
33 <refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
38 <funcsynopsisinfo>#include <elogind/sd-id128.h></funcsynopsisinfo>
41 <funcdef>char *<function>sd_id128_to_string</function></funcdef>
42 <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
46 <funcdef>int <function>sd_id128_from_string</function></funcdef>
47 <paramdef>const char *<parameter>s</parameter>, sd_id128_t *<parameter>ret</parameter></paramdef>
54 <title>Description</title>
56 <para><function>sd_id128_to_string()</function> formats a 128-bit
57 ID as a character string. It expects the ID and a string array
58 capable of storing 33 characters. The ID will be formatted as 32
59 lowercase hexadecimal digits and be terminated by a
60 <constant>NUL</constant> byte.</para>
62 <para><function>sd_id128_from_string()</function> implements the reverse operation: it takes a 33 character string
63 with 32 hexadecimal digits (either lowercase or uppercase, terminated by <constant>NUL</constant>) and parses them
64 back into a 128-bit ID returned in <parameter>ret</parameter>. Alternatively, this call can also parse a
65 37-character string with a 128-bit ID formatted as RFC UUID. If <parameter>ret</parameter> is passed as NULL the
66 function will validate the passed ID string, but not actually return it in parsed form.</para>
68 <para>For more information about the <literal>sd_id128_t</literal>
70 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
71 Note that these calls operate the same way on all architectures,
72 i.e. the results do not depend on endianness.</para>
74 <para>When formatting a 128-bit ID into a string, it is often
75 easier to use a format string for
76 <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
77 This is easily done using the
78 <function>SD_ID128_FORMAT_STR</function> and
79 <function>SD_ID128_FORMAT_VAL()</function> macros. For more
81 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
85 <title>Return Value</title>
87 <para><function>sd_id128_to_string()</function> always succeeds
88 and returns a pointer to the string array passed in.
89 <function>sd_id128_from_string</function> returns 0 on success, in
90 which case <parameter>ret</parameter> is filled in, or a negative
91 errno-style error code.</para>
94 <xi:include href="libelogind-pkgconfig.xml" />
97 <title>See Also</title>
100 <!-- 0 /// elogind is in section 8
101 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
103 <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
105 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
106 <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>