GNU Combine is a tool for working with record-oriented data files. The biggest thing it does is to expand on the join utility by allowing multiple keys in the join, working with more than one file to match to a base data file, working with unsorted files and providing a variety of flagging and aggregation options to summarize the results of the match. It is also extensible with Guile, so that you can do what you need to do at any point in the processing to adjust what's coming in or going out.
Combine can be found on the main GNU ftp server: http://ftp.gnu.org/gnu/combine/ (via HTTP) and ftp://ftp.gnu.org/gnu/combine/ (via FTP). It can also be found on the GNU mirrors; please use a mirror if possible.
Documentation for Combine is available online, as is documentation for most GNU software. You may also find more information about combine by running info combine or man combine, or by looking at /usr/share/doc/combine/, /usr/local/doc/combine/, or similar directories on your system. A brief summary is available by running combine --help.
Combine has the following mailing lists:
Security reports that should not be made immediately public can be sent directly to the maintainer. If there is no response to an urgent issue, you can escalate to the general security mailing list for advice.
Development of Combine, and GNU in general, is a volunteer effort, and you can contribute. For information, please read How to help GNU. If you'd like to get involved, it's a good idea to join the discussion mailing list (see above).
Combine is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
The Free Software Foundation is the principal organizational sponsor of the GNU Operating System. Support GNU and the FSF by buying manuals and gear, joining the FSF as an associate member, or making a donation, either directly to the FSF or via Flattr.