<literal>options</literal> this must be specified in list notation. The commands
are invoked in order using <filename>/bin/sh</filename>; should any fail APT
will abort. APT will pass the filenames of all .deb files it is going to
- install to the commands, one per line on standard input.</para>
+ install to the commands, one per line on the requested file descriptor, defaulting
+ to standard input.</para>
<para>Version 2 of this protocol dumps more information, including the
protocol version, the APT configuration space and the packages, files
<literal>DPkg::Tools::options::<replaceable>cmd</replaceable>::Version</literal>
accordingly, the default being version 1. If APT isn't supporting the requested
version it will send the information in the highest version it has support for instead.
- </para></listitem>
+ </para>
+
+ <para>The file descriptor to be used to send the information can be requested with
+ <literal>DPkg::Tools::options::<replaceable>cmd</replaceable>::InfoFD</literal>
+ which defaults to <literal>0</literal> for standard input and is available since
+ version 0.9.11. Support for the option can be detected by looking for the environment
+ variable <envar>APT_HOOK_INFO_FD</envar> which contains the number of the used
+ file descriptor as a confirmation.</para>
+ </listitem>
</varlistentry>
<varlistentry><term><option>Run-Directory</option></term>