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
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2012 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  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> formats a 128-bit
  72     ID as a character string. It expects the ID and a string array
  73     capable of storing 33 characters. The ID will be formatted as 32
  74     lowercase hexadecimal digits and be terminated by a
  75     <constant>NUL</constant> byte.</para>
  76
  77     <para><function>sd_id128_from_string()</function> implements the
  78     reverse operation: it takes a 33 character string with 32
  79     hexadecimal digits (either lowercase or uppercase, terminated by
  80     <constant>NUL</constant>) and parses them back into a 128-bit ID
  81     returned in <parameter>ret</parameter>. Alternatively, this call
  82     can also parse a 37-character string with a 128-bit ID formatted
  83     as RFC UUID.</para>
  84
  85     <para>For more information about the <literal>sd_id128_t</literal>
  86     type see
  87     <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  88     Note that these calls operate the same way on all architectures,
  89     i.e. the results do not depend on endianness.</para>
  90
  91     <para>When formatting a 128-bit ID into a string, it is often
  92     easier to use a format string for
  93     <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  94     This is easily done using the
  95     <function>SD_ID128_FORMAT_STR</function> and
  96     <function>SD_ID128_FORMAT_VAL()</function> macros. For more
  97     information see
  98     <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  99   </refsect1>
 100
 101   <refsect1>
 102     <title>Return Value</title>
 103
 104     <para><function>sd_id128_to_string()</function> always succeeds
 105     and returns a pointer to the string array passed in.
 106     <function>sd_id128_from_string</function> returns 0 on success, in
 107     which case <parameter>ret</parameter> is filled in, or a negative
 108     errno-style error code.</para>
 109   </refsect1>
 110
 111   <refsect1>
 112     <title>Notes</title>
 113
 114     <para>The <function>sd_id128_to_string()</function> and
 115     <function>sd_id128_from_string()</function> interfaces are
 116     available as a shared library, which can be compiled and linked to
 117     with the
 118     <literal>libsystemd</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 119     file.</para>
 120   </refsect1>
 121
 122   <refsect1>
 123     <title>See Also</title>
 124
 125     <para>
 126       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 127       <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 128       <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 129     </para>
 130   </refsect1>
 131
 132 </refentry>