/usr/share/help/C/gthumb/batch-scripts.page is in gthumb-data 3:3.4.3-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | <page xmlns="http://projectmallard.org/1.0/" type="topic"
id="gthumb-batch-scripts">
  <info>
    <link type="guide" xref="index#batch" />
  </info>
  <title>User-Defined Scripts</title>
  <p>To define a script (a command-line sequence that <app>gThumb</app> will
  execute on your files), click the <gui>Tools</gui> button on the main toolbar, 
  and select <guiseq><gui>Tools</gui><gui>Personalize</gui></guiseq>.</p>
  <p>TODO: further documentation is need here.</p>
</page>
 |