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b82f58bfe3
Sometimes it's useful to provide a default value during an environment
expansion, if the environment variable isn't already set.
For instance $XDG_DATA_DIRS is suppose to default to:
/usr/local/share/:/usr/share/
if it's not yet set. That means callers wishing to augment
XDG_DATA_DIRS need to manually add those two values.
This commit changes replace_env to support the following shell
compatible default value syntax:
XDG_DATA_DIRS=/foo:${XDG_DATA_DIRS:-/usr/local/share/:/usr/share}
Likewise, it's useful to provide an alternate value during an
environment expansion, if the environment variable isn't already set.
For instance, $LD_LIBRARY_PATH will inadvertently search the current
working directory if it starts or ends with a colon, so the following
is usually wrong:
LD_LIBRARY_PATH=/foo/lib:${LD_LIBRARY_PATH}
To address that, this changes replace_env to support the following
shell compatible alternate value syntax:
LD_LIBRARY_PATH=/foo/lib${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}
[zj: gate the new syntax under REPLACE_ENV_ALLOW_EXTENDED switch, so
existing callers are not modified.]
123 lines
4.9 KiB
XML
123 lines
4.9 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2016 Red Hat, Inc.
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Copyright 2017 Zbigniew Jędrzejewski-Szmek
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="environment.d" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>environment.d</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Ray</firstname>
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<surname>Strode</surname>
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<email>rstrode@redhat.com</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>environment.d</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>environment.d</refname>
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<refpurpose>Definition of user session environment</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>~/.config/environment.d/*.conf</filename></para>
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<para><filename>/etc/environment.d/*.conf</filename></para>
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<para><filename>/run/environment.d/*.conf</filename></para>
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<para><filename>/usr/lib/environment.d/*.conf</filename></para>
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<para><filename>/etc/environment</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>The <filename>environment.d</filename> directories contain a list of "global" environment
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variable assignments for the user environment.
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<citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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parses them and updates the environment exported by the systemd user instance to the services it
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starts.</para>
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<para>It is recommended to use numerical prefixes for file names to simplify ordering.</para>
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<para>For backwards compatibility, a symlink to <filename>/etc/environment</filename> is
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installed, so this file is also parsed.</para>
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</refsect1>
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<xi:include href="standard-conf.xml" xpointer="confd" />
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<refsect1>
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<title>Configuration Format</title>
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<para>The configuration files contain a list of
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<literal><replaceable>KEY</replaceable>=<replaceable>VALUE</replaceable></literal> environment
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variable assignments, separated by newlines. The right hand side of these assignments may
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reference previously defined environment variables, using the <literal>${OTHER_KEY}</literal>
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and <literal>$OTHER_KEY</literal> format. It is also possible to use
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<literal>${<replaceable>FOO</replaceable>:-<replaceable>DEFAULT_VALUE</replaceable>}</literal>
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to expand in the same way as <literal>${<replaceable>FOO</replaceable>}</literal> unless the
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expansion would be empty, in which case it expands to <replaceable>DEFAULT_VALUE</replaceable>,
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and use
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<literal>${<replaceable>FOO</replaceable>:+<replaceable>ALTERNATE_VALUE</replaceable>}</literal>
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to expand to <replaceable>ALTERNATE_VALUE</replaceable> as long as
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<literal>${<replaceable>FOO</replaceable>}</literal> would have expanded to a non-empty value.
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No other elements of shell syntax are supported.</para>
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<para>Each<replaceable>KEY</replaceable> must be a valid variable name. Empty lines
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and lines beginning with the comment character <literal>#</literal> are ignored.</para>
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<refsect2>
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<title>Example</title>
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<example>
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<title>Setup environment to allow access to a program installed in
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<filename noindex='true'>/opt/foo</filename></title>
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<para><filename>/etc/environment.d/60-foo.conf</filename>:
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</para>
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<programlisting>
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FOO_DEBUG=force-software-gl,log-verbose
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PATH=/opt/foo/bin:$PATH
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LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}/opt/foo/lib
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XDG_DATA_DIRS=/opt/foo/share:${XDG_DATA_DIRS:-/usr/local/share/:/usr/share/}
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</programlisting>
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</example>
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</refsect2>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.environment-generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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