<?xml version="1.0"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
- "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
-<!ENTITY % entities SYSTEM "custom-entities.ent" >
-%entities;
-]>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refsect1>
- <title>Environment</title>
-
- <variablelist class='environment-variables'>
- <varlistentry id='pager'>
- <term><varname>$SYSTEMD_PAGER</varname></term>
-
- <listitem><para>Pager to use when
- <option>--no-pager</option> is not given;
- overrides <varname>$PAGER</varname>. Setting
- this to an empty string or the value
- <literal>cat</literal> is equivalent to passing
- <option>--no-pager</option>.</para></listitem>
- </varlistentry>
-
- <varlistentry id='less'>
- <term><varname>$SYSTEMD_LESS</varname></term>
-
- <listitem><para>Override the default
- options passed to
- <command>less</command>
- (<literal>FRSXMK</literal>).</para></listitem>
- </varlistentry>
- </variablelist>
+ <title>Environment</title>
+
+ <variablelist class='environment-variables'>
+ <varlistentry id='pager'>
+ <term><varname>$SYSTEMD_PAGER</varname></term>
+
+ <listitem><para>Pager to use when <option>--no-pager</option> is not given; overrides
+ <varname>$PAGER</varname>. If neither <varname>$SYSTEMD_PAGER</varname> nor <varname>$PAGER</varname> are set, a
+ set of well-known pager implementations are tried in turn, including
+ <citerefentry project='man-pages'><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry> and
+ <citerefentry project='man-pages'><refentrytitle>more</refentrytitle><manvolnum>1</manvolnum></citerefentry>, until one is found. If
+ no pager implementation is discovered no pager is invoked. Setting this environment variable to an empty string
+ or the value <literal>cat</literal> is equivalent to passing <option>--no-pager</option>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='less'>
+ <term><varname>$SYSTEMD_LESS</varname></term>
+
+ <listitem><para>Override the options passed to <command>less</command> (by default
+ <literal>FRSXMK</literal>).</para>
+
+ <para>Users might want to change two options in particular:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><option>K</option></term>
+
+ <para>This option instructs the pager to exit immediately when
+ <keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo> is pressed. To allow
+ <command>less</command> to handle <keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo>
+ itself to switch back to the pager command prompt, unset this option.</para>
+
+ <para>If the value of <varname>$SYSTEMD_LESS</varname> does not include <literal>K</literal>,
+ and the pager that is invoked is <command>less</command>,
+ <keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo> will be ignored by the
+ executable, and needs to be handled by the pager.</para>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>X</option></term>
+
+ <para>This option instructs the pager to not send termcap initialization and deinitialization
+ strings to the terminal. It is set by default to allow command output to remain visible in the
+ terminal even after the pager exits. Nevertheless, this prevents some pager functionality from
+ working, in particular paged output cannot be scrolled with the mouse.</para>
+ </varlistentry>
+ </variablelist>
+
+ <para>See
+ <citerefentry project='man-pages'><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ for more discussion.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='lesscharset'>
+ <term><varname>$SYSTEMD_LESSCHARSET</varname></term>
+
+ <listitem><para>Override the charset passed to <command>less</command> (by default <literal>utf-8</literal>, if
+ the invoking terminal is determined to be UTF-8 compatible).</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='colors'>
+ <term><varname>$SYSTEMD_COLORS</varname></term>
+
+ <listitem><para>The value must be a boolean. Controls whether colorized output should be
+ generated. This can be specified to override the decision that <command>systemd</command> makes based
+ on <varname>$TERM</varname> and what the console is connected to.</para>
+ </listitem>
+ </varlistentry>
+
+ <!-- This is not documented on purpose, because it is not clear if $NO_COLOR will become supported
+ widely enough. So let's provide support, but without advertising this.
+ <varlistentry id='no-color'>
+ <term><varname>$NO_COLOR</varname></term>
+
+ <listitem><para>If set (to any value), and <varname>$SYSTEMD_COLORS</varname> is not set, equivalent to
+ <option>SYSTEMD_COLORS=0</option>. See <ulink url="https://no-color.org/">no-color.org</ulink>.</para>
+ </listitem>
+ </varlistentry>
+ -->
+
+ <varlistentry id='urlify'>
+ <term><varname>$SYSTEMD_URLIFY</varname></term>
+
+ <listitem><para>The value must be a boolean. Controls whether clickable links should be generated in
+ the output for terminal emulators supporting this. This can be specified to override the decision that
+ <command>systemd</command> makes based on <varname>$TERM</varname> and other conditions.</para>
+ </listitem>
+ </varlistentry>
+
+ </variablelist>
</refsect1>