dnsname/dnsnamex - does a reverse lookup for the IP address

dnsname a.b.c.d

dnsnamex a.b.c.d

dnsname does a reverse lookup for the IP address a.b.c.d. It 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.

dnsnamex, works like dnsname(1) but prints all of the names that an IP address maps to, instead of just the first one like dnsname does.

There is also a dnsfilter(1) program that reads IP addresses from its input and performs many reverse lookups in parallel.

Normally dnsname exits 0. If dnsname encounters a temporary problem that prevents it from determining the domain name, it prints an error message and exits 111. It also exits 111 if it is not able to write the ip address to descriptor 1.

dnsip(1), dnsipq(1), dnsmx(1), dnstxt(1), dnsqr(1), dnsq(1), dnstrace(1), http://cr.yp.to/djbdns.html