Host is a very powerful DNS query and testing command-line tool. Major
differences with the ancient version of the program with the same name
that's included in the BIND-4 and BIND-8 distributions:

 - Major overhaul of the entire code including rigid error checking,
   and verbose error messages. Several sections have been rewritten
   from scratch. Documentation has been added. Syntax extended.
 - It is now possible to do recursive listings into delegated zones.
 - Maintain resource record statistics and host count during zone listings.
 - Check for various extraneous conditions during zone listings.
 - Check for illegal domain names containing invalid characters.
 - Verify that certain domain names represent canonical host names.
 - Perform ttl consistency checking during zone listings.
 - Exploit multiple server addresses if available.
 - Option to exploit only primary server for zone transfers.
 - Option to exclude info from names that do not reside in a zone.
 - Implement timeout handling during connect and read.
 - Write resource record output to optional log file.
 - Special MB tracing by recursively expanding MR and MG records.
 - Special mode to check SOA records at each nameserver for a zone.
 - Special mode to check reverse mappings of host addresses.
 - Configurable default options in HOST_DEFAULTS environment variable.
 - Implement new resource record types from RFCs 1183, 1348, 1664, 1712,
   1876 and 1886. Basic experimental NSAP support as defined in RFC 1637.

Homepage:
http://www.weird.com/~woods/projects/host.html
