man: systemctl list-timers: Provide sample output and document it. (#5463)

As with `systemctl list-sockets` and `systemctl status`, we provide a sample
output for `systemctl list-timers` and document what the columns mean.

diff --git a/man/systemctl.xml b/man/systemctl.xml
index d0b39d771bd969d4dbd3071d8c809adf7c17d1ec..22ff9494d6ddbd45eb14d84178bdf091db97ac25 100644 (file)
--- a/man/systemctl.xml
+++ b/man/systemctl.xml
@@ -712,8 +712,23 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
           <listitem>
             <para>List timer units currently in memory, ordered by the time they elapse next. If one or more
             <replaceable>PATTERN</replaceable>s are specified, only units matching one of them are shown.
+            Produces output similiar to
+            <programlisting>
+NEXT                         LEFT          LAST                         PASSED     UNIT                         ACTIVATES
+n/a                          n/a           Thu 2017-02-23 13:40:29 EST  3 days ago ureadahead-stop.timer        ureadahead-stop.service
+Sun 2017-02-26 18:55:42 EST  1min 14s left Thu 2017-02-23 13:54:44 EST  3 days ago systemd-tmpfiles-clean.timer systemd-tmpfiles-clean.service
+Sun 2017-02-26 20:37:16 EST  1h 42min left Sun 2017-02-26 11:56:36 EST  6h ago     apt-daily.timer              apt-daily.service
+Sun 2017-02-26 20:57:49 EST  2h 3min left  Sun 2017-02-26 11:56:36 EST  6h ago     snapd.refresh.timer          snapd.refresh.service
+            </programlisting>
             </para>
 
+            <para><emphasis>NEXT</emphasis> shows the next time the timer will run.</para>
+            <para><emphasis>LEFT</emphasis> shows how long till the next time the timer runs.</para>
+            <para><emphasis>LAST</emphasis> shows the last time the timer ran.</para>
+            <para><emphasis>PASSED</emphasis> shows has long as passed since the timer laset ran.</para>
+            <para><emphasis>UNIT</emphasis> shows the name of the timer</para>
+            <para><emphasis>ACTIVATES</emphasis> shows the the name the service the timer activates when it runs.</para>
+
             <para>Also see <option>--all</option> and <option>--state=</option>.</para>
           </listitem>
         </varlistentry>