systemd/man/sd_id128_to_string.xml

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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Copyright 2012 Lennart Poettering
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<refentry id="sd_id128_to_string">
<refentryinfo>
<title>sd_id128_to_string</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_id128_to_string</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_id128_to_string</refname>
<refname>sd_id128_from_string</refname>
<refpurpose>Format or parse 128-bit IDs as strings</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>char* <function>sd_id128_to_string</function></funcdef>
<paramdef>sd_id128_t <parameter>id</parameter>, char <parameter>s</parameter>[33]</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_id128_from_string</function></funcdef>
<paramdef>const char* <parameter>s</parameter>, sd_id128_t* <parameter>ret</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_id128_to_string()</function>
formats a 128-bit ID as a character string. It expects
the ID and a string array capable of storing 33
characters. The ID will be formatted as 32 lowercase
hexadecimal digits and be terminated by a
<constant>NUL</constant> byte.</para>
<para><function>sd_id128_from_string()</function>
implements the reverse operation: it takes a 33
character string with 32 hexadecimal digits (either
lowercase or uppercase, terminated by
<constant>NUL</constant>) and parses them back into a
128-bit ID returned in
<parameter>ret</parameter>. Alternatively, this call
can also parse a 37-character string with a 128-bit ID
formatted as RFC UUID.</para>
<para>For more information about the
<literal>sd_id128_t</literal> type see
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Note
that these calls operate the same way on all
architectures, i.e. the results do not depend on
endianness.</para>
<para>When formatting a 128-bit ID into a string, it is
often easier to use a format string for
<citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>. This
is easily done using the
<function>SD_ID128_FORMAT_STR</function> and
<function>SD_ID128_FORMAT_VAL()</function> macros. For
more information see
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para><function>sd_id128_to_string()</function> always
succeeds and returns a pointer to the string array
passed in. <function>sd_id128_from_string</function>
returns 0 on success, in which case
<parameter>ret</parameter> is filled in, or a negative
errno-style error code.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_id128_to_string()</function>
and <function>sd_id128_from_string()</function> interfaces are
available as a shared library, which can be compiled and
linked to with the <literal>libsystemd</literal> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>