This is the FreeBSD whois client, with two patches.

whois-aunic-port.diff - Adds the missing AUNIC option (-u) and adds
                        an option to query a whois server on a specific
                        port (needed for many rwhois servers).
whois-linux-solaris.diff - Allows it to compile on Linux or Solaris systems.
                           This patch must be applied before the previous
                           one.

FreeBSD:  This whois client is provided, apply the patch to
          /usr/src/usr.bin/whois, make, and make install

Linux:  Apply at least the second patch, and run gcc -o bsdwhois whois.c.
        Install bsdwhois somewhere in the path.

Solaris:  Apply at least the second patch, and run
          gcc -o bsdwhois whois.c -lsocket -lnsl.  Install bsdwhois
          somewhere in the path.

Cygwin:  Sorry, it will not compile on Cygwin, even with the second patch.

Other systems have not been tested.

The BSD whois client is superior to many others as it provides a number
of shortcuts for admins.  whois -a will query ARIN, whois -r will query
RIPE, and so on.  Refer to the manpage for additional information.