<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//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/>.
--->
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="sd-id128"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd-id128</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<refname>sd-id128</refname>
<refname>sd_id128_t</refname>
<refname>SD_ID128_MAKE</refname>
+ <refname>SD_ID128_MAKE_STR</refname>
+ <refname>SD_ID128_NULL</refname>
<refname>SD_ID128_CONST_STR</refname>
<refname>SD_ID128_FORMAT_STR</refname>
+ <refname>SD_ID128_UUID_FORMAT_STR</refname>
<refname>SD_ID128_FORMAT_VAL</refname>
<refname>sd_id128_equal</refname>
+ <refname>sd_id128_is_null</refname>
<refpurpose>APIs for processing 128-bit IDs</refpurpose>
</refnamediv>
union type:</para>
<programlisting>typedef union sd_id128 {
- uint8_t bytes[16];
- uint64_t qwords[2];
+ uint8_t bytes[16];
+ uint64_t qwords[2];
} sd_id128_t;</programlisting>
<para>This union type allows accessing the 128-bit ID as 16
<programlisting>#define SD_MESSAGE_COREDUMP SD_ID128_MAKE(fc,2e,22,bc,6e,e6,47,b6,b9,07,29,ab,34,a2,50,b1)</programlisting>
+ <para><function>SD_ID128_NULL</function> may be used to refer to the 128bit ID consisting of only NUL
+ bytes.</para>
+
+ <para><function>SD_ID128_MAKE_STR()</function> is similar to <function>SD_ID128_MAKE()</function>, but creates a
+ <type>const char*</type> expression that can be conveniently used in message formats and such:</para>
+
+ <programlisting>#include <stdio.h>
+#define SD_MESSAGE_COREDUMP_STR SD_ID128_MAKE_STR(fc,2e,22,bc,6e,e6,47,b6,b9,07,29,ab,34,a2,50,b1)
+
+int main(int argc, char **argv) {
+ puts("Match for coredumps: MESSAGE_ID=" SD_MESSAGE_COREDUMP_STR);
+}
+ </programlisting>
+
<para><function>SD_ID128_CONST_STR()</function> may be used to
convert constant 128-bit IDs into constant strings for output. The
following example code will output the string
"fc2e22bc6ee647b6b90729ab34a250b1":</para>
<programlisting>int main(int argc, char *argv[]) {
- puts(SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP));
+ puts("Match for coredumps: %s", SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP));
}</programlisting>
- <para><function>SD_ID128_FORMAT_STR</function> and
+ <para><function>SD_ID128_FORMAT_STR()</function> and
<function>SD_ID128_FORMAT_VAL()</function> may be used to format a
128-bit ID in a
<citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
format string, as shown in the following example:</para>
<programlisting>int main(int argc, char *argv[]) {
- sd_id128_t id;
- id = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
- printf("The ID encoded in this C file is " SD_ID128_FORMAT_STR ".\n", SD_ID128_FORMAT_VAL(id));
- return 0;
+ sd_id128_t id;
+ id = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
+ printf("The ID encoded in this C file is " SD_ID128_FORMAT_STR ".\n", SD_ID128_FORMAT_VAL(id));
+ return 0;
}</programlisting>
+ <para><function>SD_ID128_UUID_FORMAT_STR()</function> is similar to
+ <function>SD_ID128_FORMAT_STR()</function> but includes separating hyphens to conform to the
+ "<ulink url="https://en.wikipedia.org/wiki/Universally_unique_identifier#Format">canonical representation</ulink>".
+ </para>
+
<para>Use <function>sd_id128_equal()</function> to compare two 128-bit IDs:</para>
<programlisting>int main(int argc, char *argv[]) {
- sd_id128_t a, b, c;
- a = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
- b = SD_ID128_MAKE(f2,28,88,9c,5f,09,44,15,9d,d7,04,77,58,cb,e7,3e);
- c = a;
- assert(sd_id128_equal(a, c));
- assert(!sd_id128_equal(a, b));
- return 0;
+ sd_id128_t a, b, c;
+ a = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
+ b = SD_ID128_MAKE(f2,28,88,9c,5f,09,44,15,9d,d7,04,77,58,cb,e7,3e);
+ c = a;
+ assert(sd_id128_equal(a, c));
+ assert(!sd_id128_equal(a, b));
+ return 0;
+}</programlisting>
+
+ <para>Use <function>sd_id128_is_null()</function> to check if an 128bit ID consists of only NUL bytes:</para>
+
+ <programlisting>int main(int argc, char *argv[]) {
+ assert(sd_id128_is_null(SD_ID128_NULL));
}</programlisting>
<para>Note that new, randomized IDs may be generated with
- <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
- <option>--new-id</option> option.</para>
+ <citerefentry><refentrytitle>systemd-id128</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
+ <command>new</command> command.</para>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
projects / thirdparty / systemd.git / blobdiff