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diff --git a/man/common-variables.xml b/man/common-variables.xml new file mode 100644 index 0000000..0e220b3 --- /dev/null +++ b/man/common-variables.xml @@ -0,0 +1,202 @@ +<?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='log-level'> + <term><varname>$SYSTEMD_LOG_LEVEL</varname></term> + + <listitem><para id='log-level-body'>The maximum log level of emitted messages (messages with a higher + log level, i.e. less important ones, will be suppressed). Either one of (in order of decreasing + importance) <constant>emerg</constant>, <constant>alert</constant>, <constant>crit</constant>, + <constant>err</constant>, <constant>warning</constant>, <constant>notice</constant>, + <constant>info</constant>, <constant>debug</constant>, or an integer in the range 0…7. See + <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> + for more information.</para> + </listitem> + </varlistentry> + + <varlistentry id='log-color'> + <term><varname>$SYSTEMD_LOG_COLOR</varname></term> + + <listitem><para id='log-color-body'>A boolean. If true, messages written to the tty will be colored + according to priority.</para> + + <para>This setting is only useful when messages are written directly to the terminal, because + <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> and + other tools that display logs will color messages based on the log level on their own.</para> + </listitem> + </varlistentry> + + <varlistentry id='log-time'> + <term><varname>$SYSTEMD_LOG_TIME</varname></term> + + <listitem><para id='log-time-body'>A boolean. If true, console log messages will be prefixed with a + timestamp.</para> + + <para>This setting is only useful when messages are written directly to the terminal or a file, because + <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> and + other tools that display logs will attach timestamps based on the entry metadata on their own.</para> + </listitem> + </varlistentry> + + <varlistentry id='log-location'> + <term><varname>$SYSTEMD_LOG_LOCATION</varname></term> + + <listitem><para id='log-location-body'>A boolean. If true, messages will be prefixed with a filename + and line number in the source code where the message originates.</para> + + <para>Note that the log location is often attached as metadata to journal entries anyway. Including it + directly in the message text can nevertheless be convenient when debugging programs.</para> + </listitem> + </varlistentry> + + <varlistentry id='log-tid'> + <term><varname>$SYSTEMD_LOG_TID</varname></term> + + <listitem><para id='log-tid-body'>A boolean. If true, messages will be prefixed with the current + numerical thread ID (TID).</para> + + <para>Note that the this information is attached as metadata to journal entries anyway. Including it + directly in the message text can nevertheless be convenient when debugging programs.</para> + </listitem> + </varlistentry> + + <varlistentry id='log-target'> + <term><varname>$SYSTEMD_LOG_TARGET</varname></term> + + <listitem><para id='log-target-body'>The destination for log messages. One of + <constant>console</constant> (log to the attached tty), <constant>console-prefixed</constant> (log to + the attached tty but with prefixes encoding the log level and "facility", see <citerefentry + project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <constant>kmsg</constant> (log to the kernel circular log buffer), <constant>journal</constant> (log to + the journal), <constant>journal-or-kmsg</constant> (log to the journal if available, and to kmsg + otherwise), <constant>auto</constant> (determine the appropriate log target automatically, the default), + <constant>null</constant> (disable log output).</para> + <!-- <constant>syslog</constant>, <constant>syslog-or-kmsg</constant> are deprecated --> + </listitem> + </varlistentry> + + <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> + + <para>Note: if <varname>$SYSTEMD_PAGERSECURE</varname> is not set, <varname>$SYSTEMD_PAGER</varname> + (as well as <varname>$PAGER</varname>) will be silently ignored.</para></listitem> + </varlistentry> + + <varlistentry id='less'> + <term><varname>$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>$SYSTEMD_PAGERSECURE</varname> is not set at all, pagers which are not known to implement + secure mode will not be used. (Currently only + <citerefentry project='man-pages'><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry> + implements secure mode.)</para> + + <para>Note: when commands are invoked with elevated privileges, for example under <citerefentry + project='man-pages'><refentrytitle>sudo</refentrytitle><manvolnum>8</manvolnum></citerefentry> or + <citerefentry + project='die-net'><refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum></citerefentry>, care + must be taken to ensure that unintended interactive features are not enabled. "Secure" mode for the + pager may be enabled automatically as describe above. Setting <varname>SYSTEMD_PAGERSECURE=0</varname> + or not removing it from the inherited environment allows the user to invoke arbitrary commands. Note + that if the <varname>$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>$SYSTEMD_COLORS</varname></term> + + <listitem><para>Takes a boolean argument. When true, <command>systemd</command> and related utilities + will use colors in their output, otherwise the output will be monochrome. Additionally, the variable can + take one of the following special values: <literal>16</literal>, <literal>256</literal> to restrict the use + of colors to the base 16 or 256 ANSI colors, respectively. This can be specified to override the automatic + decision based on <varname>$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> |