<?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">
-
-<!--
- SPDX-License-Identifier: LGPL-2.1+
-
- This file is part of systemd.
-
- Copyright 2010 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-or-later -->
<refentry id="systemd.time">
<refentryinfo>
<title>systemd.time</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
understood:</para>
<itemizedlist>
- <listitem><para>usec, us</para></listitem>
+ <listitem><para>usec, us, µs</para></listitem>
<listitem><para>msec, ms</para></listitem>
<listitem><para>seconds, second, sec, s</para></listitem>
<listitem><para>minutes, minute, min, m</para></listitem>
1y 12month
55s500ms
300ms20s 5day</programlisting>
+
+ <para>One can use the <command>timespan</command> command of
+ <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ to normalise a textual time span for testing and validation purposes.</para>
+
+ <para>Internally, systemd generally operates with microsecond time granularity, while the default time
+ unit in user-configurable time spans is usually seconds (see above). This disparity becomes visible when
+ comparing the same settings in the (high-level) unit file syntax with the matching (more low-level) D-Bus
+ properties (which are what
+ <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
+ <command>show</command> command displays). The former typically are suffixed with <literal>…Sec</literal>
+ to indicate the default unit of seconds, the latter are typically suffixed with <literal>…USec</literal>
+ to indicate the underlying low-level time unit, even if they both encapsulate the very same
+ settings.</para>
</refsect1>
<refsect1>
<refsect1>
<title>Parsing Timestamps</title>
- <para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless it is given
- as the literal string <literal>UTC</literal> (for the UTC timezone), or is specified to be the locally configured
- timezone, or the timezone name in the IANA timezone database format. The complete list of timezones
- supported on your system can be obtained using the <literal>timedatectl list-timezones</literal>
- (see <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
- Using IANA format is recommended over local timezone names, as less prone to errors (eg: with local timezone it's possible to
- specify daylight saving time in winter, while it's incorrect). The weekday specification is optional, but when
- the weekday is specified, it must either be in the abbreviated (<literal>Wed</literal>) or non-abbreviated
- (<literal>Wednesday</literal>) English language form (case does not matter), and is not subject to the locale
- choice of the user. Either the date, or the time part may be omitted, in which case the current date or 00:00:00,
- respectively, is assumed. The seconds component of the time may also be omitted, in which case ":00" is
- assumed. Year numbers may be specified in full or may be abbreviated (omitting the century).</para>
+ <para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless
+ it is given as the literal string <literal>UTC</literal> (for the UTC timezone), or is specified to be
+ the locally configured timezone, or the timezone name in the IANA timezone database format. The complete
+ list of timezones supported on your system can be obtained using the <literal>timedatectl
+ list-timezones</literal> (see
+ <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Using
+ IANA format is recommended over local timezone names, as less prone to errors (e.g. with local timezone
+ it's possible to specify daylight saving time in winter, even though that is not correct). The weekday
+ specification is optional, but when the weekday is specified, it must either be in the abbreviated
+ (<literal>Wed</literal>) or non-abbreviated (<literal>Wednesday</literal>) English language form (case
+ does not matter), and is not subject to the locale choice of the user. Either the date, or the time part
+ may be omitted, in which case the current date or 00:00:00, respectively, is assumed. The seconds
+ component of the time may also be omitted, in which case ":00" is assumed. Year numbers may be specified
+ in full or may be abbreviated (omitting the century).</para>
<para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
the week.</para>
evaluated relative to the UNIX time epoch 1st Jan, 1970,
00:00.</para>
- <para>Examples for valid timestamps and their normalized form
- (assuming the current time was 2012-11-23 18:15:22 and the timezone
- was UTC+8, for example TZ=Asia/Shanghai):</para>
+ <para>Examples for valid timestamps and their normalized form (assuming the current time was 2012-11-23
+ 18:15:22 and the timezone was UTC+8, for example <literal>TZ=:Asia/Shanghai</literal>):</para>
<programlisting> Fri 2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
<programlisting>2 months 5 days ago</programlisting>
<para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).</para>
+
+ <para>Use the <command>timestamp</command> command of
+ <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry> to
+ validate and normalize timestamps for testing purposes.</para>
</refsect1>
<refsect1>
continuous weekdays. <literal>,</literal> and <literal>..</literal>
may be combined freely.</para>
- <para>In the date and time specifications, any component may be
- specified as <literal>*</literal> in which case any value will
- match. Alternatively, each component can be specified as a list of
- values separated by commas. Values may be suffixed with
- <literal>/</literal> and a repetition value, which indicates that
- the value itself and the value plus all multiples of the repetition value
- are matched. Two values separated by <literal>..</literal> may be used
- to indicate a range of values; ranges may also be followed with
- <literal>/</literal> and a repetition value.</para>
+ <para>In the date and time specifications, any component may be specified as <literal>*</literal> in
+ which case any value will match. Alternatively, each component can be specified as a list of values
+ separated by commas. Values may be suffixed with <literal>/</literal> and a repetition value, which
+ indicates that the value itself and the value plus all multiples of the repetition value are matched.
+ Two values separated by <literal>..</literal> may be used to indicate a range of values; ranges may also
+ be followed with <literal>/</literal> and a repetition value, in which case the expression matches all
+ times starting with the start value, and continuing with all multiples of the repetition value relative
+ to the start value, ending at the end value the latest.</para>
<para>A date specification may use <literal>~</literal> to indicate the
last day(s) in a month. For example, <literal>*-02~03</literal> means
<para>Use the <command>calendar</command> command of
<citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
- calendar event would elapse next.</para>
+ calendar event would occur next.</para>
</refsect1>
<refsect1>
projects / thirdparty / systemd.git / blobdiff