NAME
dnsname - does a reverse lookup for the IP address
SYNOPSIS
dnsname a.b.c.d
DESCRIPTION
dnsname prints the first domain name for
that address. If no domain names are listed in DNS, dnsname
prints a blank line. You can list several IP addresses;
dnsname prints each result on a separate line.
There is also a dnsfilter(1)
program that reads IP addresses from its input and performs many
reverse lookups in parallel.
SEE ALSO
dnsip(1),
dnsipq(1),
dnsmx(1),
dnstxt(1),
dnsqr(1),
dnsq(1),
dnstrace(1)
http://cr.yp.to/djbdns.html