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[elogind.git] / man / sd_id128_to_string.xml
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">
4
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8   Copyright 2012 Lennart Poettering
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23
24 <refentry id="sd_id128_to_string">
25
26         <refentryinfo>
27                 <title>sd_id128_to_string</title>
28                 <productname>systemd</productname>
29
30                 <authorgroup>
31                         <author>
32                                 <contrib>Developer</contrib>
33                                 <firstname>Lennart</firstname>
34                                 <surname>Poettering</surname>
35                                 <email>lennart@poettering.net</email>
36                         </author>
37                 </authorgroup>
38         </refentryinfo>
39
40         <refmeta>
41                 <refentrytitle>sd_id128_to_string</refentrytitle>
42                 <manvolnum>3</manvolnum>
43         </refmeta>
44
45         <refnamediv>
46                 <refname>sd_id128_to_string</refname>
47                 <refname>sd_id128_from_string</refname>
48                 <refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
49         </refnamediv>
50
51         <refsynopsisdiv>
52                 <funcsynopsis>
53                         <funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</funcsynopsisinfo>
54
55                         <funcprototype>
56                                 <funcdef>char* <function>sd_id128_to_string</function></funcdef>
57                                 <paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
58                         </funcprototype>
59
60                         <funcprototype>
61                                 <funcdef>int <function>sd_id128_from_string</function></funcdef>
62                                 <paramdef>const char* <parameter>s</parameter>, sd_id128_t* <parameter>ret</parameter></paramdef>
63                         </funcprototype>
64
65                 </funcsynopsis>
66         </refsynopsisdiv>
67
68         <refsect1>
69                 <title>Description</title>
70
71                 <para><function>sd_id128_to_string()</function>
72                 formats a 128-bit ID as a character string. It expects
73                 the ID and a string array capable of storing 33
74                 characters. The ID will be formatted as 32 lowercase
75                 hexadecimal digits and be terminated by a
76                 <constant>NUL</constant> byte.</para>
77
78                 <para><function>sd_id128_from_string()</function>
79                 implements the reverse operation: it takes a 33
80                 character string with 32 hexadecimal digits (either
81                 lowercase or uppercase, terminated by
82                 <constant>NUL</constant>) and parses them back into a
83                 128-bit ID returned in
84                 <parameter>ret</parameter>. Alternatively, this call
85                 can also parse a 37-character string with a 128-bit ID
86                 formatted as RFC UUID.</para>
87
88                 <para>For more information about the
89                 <literal>sd_id128_t</literal> type see
90                 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Note
91                 that these calls operate the same way on all
92                 architectures, i.e. the results do not depend on
93                 endianness.</para>
94
95                 <para>When formatting a 128-bit ID into a string, it is
96                 often easier to use a format string for
97                 <citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>. This
98                 is easily done using the
99                 <function>SD_ID128_FORMAT_STR</function> and
100                 <function>SD_ID128_FORMAT_VAL()</function> macros. For
101                 more information see
102                 <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
103         </refsect1>
104
105         <refsect1>
106                 <title>Return Value</title>
107
108                 <para><function>sd_id128_to_string()</function> always
109                 succeeds and returns a pointer to the string array
110                 passed in. <function>sd_id128_from_string</function>
111                 returns 0 on success, in which case
112                 <parameter>ret</parameter> is filled in, or a negative
113                 errno-style error code.</para>
114         </refsect1>
115
116         <refsect1>
117                 <title>Notes</title>
118
119                 <para>The <function>sd_id128_to_string()</function>
120                 and <function>sd_id128_from_string()</function> interfaces are
121                 available as a shared library, which can be compiled and
122                 linked to with the <literal>libsystemd</literal> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
123                 file.</para>
124         </refsect1>
125
126         <refsect1>
127                 <title>See Also</title>
128
129                 <para>
130                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
131                         <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
132                         <citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
133                 </para>
134         </refsect1>
135
136 </refentry>