[lug] Converting IPs to Domain Names and Vice Versa via Bash

[Jeff Schroeder]

Bill asked:

> Does anyone know if there's a simple bash command that can take a
> domain name as input and spit out its IP? Also, can I go the other
> way?

It's not a bash built-in, but you can just use 'ping':

# ping google.com
PING google.com (216.239.39.99): 56 data bytes

To do a reverse lookup, you probably want the 'dig' command (with a -x 
argument, for reverse):

# dig -x 216.239.39.99

; <<>> DiG 9.2.3 <<>> -x 216.239.39.99
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 24272
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;99.39.239.216.in-addr.arpa.    IN      PTR

;; AUTHORITY SECTION:
39.239.216.in-addr.arpa. 60     IN      SOA     ns1.google.com. 
dns-admin.google.com. 2004031201 21600 3600 1038800 60

;; Query time: 306 msec
;; SERVER: 24.221.192.5#53(24.221.192.5)
;; WHEN: Wed Jan 26 16:53:33 2005
;; MSG SIZE  rcvd: 104

HTH,
Jeff