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diff --git a/man/less-variables.xml b/man/less-variables.xml new file mode 100644 index 0000000..3b32673 --- /dev/null +++ b/man/less-variables.xml @@ -0,0 +1,124 @@ +<?xml version="1.0"?> +<!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-or-later --> + +<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>$SYSTEMD_LESS</varname></term> + + <listitem><para>Override the options passed to <command>less</command> (by default + <literal>FRSXMK</literal>).</para> + + <para>Users might want to change two options in particular:</para> + + <variablelist> + <varlistentry> + <term><option>K</option></term> + + <para>This option instructs the pager to exit immediately when + <keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo> is pressed. To allow + <command>less</command> to handle <keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo> + itself to switch back to the pager command prompt, unset this option.</para> + + <para>If the value of <varname>$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>$SYSTEMD_LESSCHARSET</varname></term> + + <listitem><para>Override the charset passed to <command>less</command> (by default <literal>utf-8</literal>, if + the invoking terminal is determined to be UTF-8 compatible).</para></listitem> + </varlistentry> + + <varlistentry id='lesssecure'> + <term><varname>$SYSTEMD_PAGERSECURE</varname></term> + + <listitem><para>Takes a boolean argument. When true, the "secure" mode of the pager is enabled; if + false, disabled. If <varname>$SYSTEMD_PAGERSECURE</varname> is not set at all, secure mode is enabled + if the effective UID is not the same as the owner of the login session, see <citerefentry + project='man-pages'><refentrytitle>geteuid</refentrytitle><manvolnum>2</manvolnum></citerefentry> and + <citerefentry><refentrytitle>sd_pid_get_owner_uid</refentrytitle><manvolnum>3</manvolnum></citerefentry>. + In secure mode, <option>LESSSECURE=1</option> will be set when invoking the pager, and the pager shall + disable commands that open or create new files or start new subprocesses. When + <varname>$SYSTEMD_PAGERSECURE</varname> is not set at all, pagers which are not known to implement + secure mode will not be used. (Currently only + <citerefentry><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry> implements + secure mode.)</para> + + <para>Note: when commands are invoked with elevated privileges, for example under <citerefentry + project='man-pages'><refentrytitle>sudo</refentrytitle><manvolnum>8</manvolnum></citerefentry> or + <citerefentry + project='die-net'><refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum></citerefentry>, care + must be taken to ensure that unintended interactive features are not enabled. "Secure" mode for the + pager may be enabled automatically as describe above. Setting <varname>SYSTEMD_PAGERSECURE=0</varname> + or not removing it from the inherited environment allows the user to invoke arbitrary commands. Note + that if the <varname>$SYSTEMD_PAGER</varname> or <varname>$PAGER</varname> variables are to be + honoured, <varname>$SYSTEMD_PAGERSECURE</varname> must be set too. It might be reasonable to completely + disable the pager using <option>--no-pager</option> instead.</para></listitem> + </varlistentry> + + <varlistentry id='colors'> + <term><varname>$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> |