man/sd_id128_to_string.xml

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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> 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 reverse operation: it takes a 33 character string
  78     with 32 hexadecimal digits (either lowercase or uppercase, terminated by <constant>NUL</constant>) and parses them
  79     back into a 128-bit ID returned in <parameter>ret</parameter>. Alternatively, this call can also parse a
  80     37-character string with a 128-bit ID formatted as RFC UUID. If <parameter>ret</parameter> is passed as NULL the
  81     function will validate the passed ID string, but not actually return it in parsed form.</para>
  82
  83     <para>For more information about the <literal>sd_id128_t</literal>
  84     type see
  85     <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  86     Note that these calls operate the same way on all architectures,
  87     i.e. the results do not depend on endianness.</para>
  88
  89     <para>When formatting a 128-bit ID into a string, it is often
  90     easier to use a format string for
  91     <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  92     This is easily done using the
  93     <function>SD_ID128_FORMAT_STR</function> and
  94     <function>SD_ID128_FORMAT_VAL()</function> macros. For more
  95     information see
  96     <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  97   </refsect1>
  98
  99   <refsect1>
 100     <title>Return Value</title>
 101
 102     <para><function>sd_id128_to_string()</function> always succeeds
 103     and returns a pointer to the string array passed in.
 104     <function>sd_id128_from_string</function> returns 0 on success, in
 105     which case <parameter>ret</parameter> is filled in, or a negative
 106     errno-style error code.</para>
 107   </refsect1>
 108
 109   <refsect1>
 110     <title>Notes</title>
 111
 112     <para>The <function>sd_id128_to_string()</function> and
 113     <function>sd_id128_from_string()</function> interfaces are
 114     available as a shared library, which can be compiled and linked to
 115     with the
 116     <literal>libsystemd</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 117     file.</para>
 118   </refsect1>
 119
 120   <refsect1>
 121     <title>See Also</title>
 122
 123     <para>
 124       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 125       <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 126       <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 127     </para>
 128   </refsect1>
 129
 130 </refentry>