<?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"> <!-- This file is part of systemd. Copyright 2012 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <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 <systemd/sd-id128.h></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 shared library, which can be compiled and linked to with the <literal>libsystemd-id128</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>