manual/substituteAll: document filtered variables

Some variables are filtered out as of #14907.
This commit is contained in:
Profpatsch 2016-05-07 13:10:09 +02:00
parent f2ec142847
commit c6cfa7a412

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@ -1169,7 +1169,17 @@ PATH=/nix/store/68afga4khv0w...-coreutils-6.12/bin
echo @foo@
</programlisting>
That is, no substitution is performed for undefined variables.</para></listitem>
That is, no substitution is performed for undefined variables.</para>
<para>Environment variables that start with an uppercase letter or an
underscore are filtered out,
to prevent global variables (like <literal>HOME</literal>) or private
variables (like <literal>__ETC_PROFILE_DONE</literal>) from accidentally
getting substituted.
The variables also have to be valid bash “names”, as
defined in the bash manpage (alphanumeric or <literal>_</literal>,
must not start with a number).</para>
</listitem>
</varlistentry>