mkhtmlindex - generate index files for HTML man pages
The mkhtmlindex program generates index files for a directory of
  HTML-formatted manual pages. It searches for files whose names are of the form
  “name.1.html”, and outputs index files
  “manindex1.html”, “manindex.2.html”, and so on,
  one for each manual volume. Empty index files will be removed. Names and
  descriptions are found by scanning the first <H2> section of each
  page.
mkhtmlindex takes only one argument: the directory to process.
This utility is currently rather specific to X manual pages. In particular, the
  format of the index files it outputs is not configurable, nor is the HTML
  formatting it expects of manual pages.
The version of the mkhtmlindex included in this X.Org Foundation release
  was originally written by David Dawes wrote as a part of XFree86.
Colin Watson wrote this manual page, originally for the Debian
    Project.