man/less-variables.xml

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<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>$PAGER</varname>. If neither <varname>$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 class='environment-variables'>
        <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>

    </variablelist>
</refsect1>