nslook-c

simple, concise ip address and hostname lookup, started 1992; status: complete, fairly stable

nslook

When I first wrote this in March 1992, I wanted a program to look up IP addresses for hosts (and the reverse) that was more concise than nslookup(1). Also, either I was not aware that for reverse lookups you could give it just the IP address in dotted decimal form, or it was actually necessary to do this dance:

> set q=ptr
> 88.199.214.85.in-addr.arpa

Anyway, I found that extremely tedious, and I also found nslookup's output too verbose in most situations.

On top of that, in some cases nslookup and its younger siblings host(1) and dig(1) weren't helpful debugging name lookup problems -- they always used the resolver library and thus DNS, which wasn't the case for most other programs, which used gethostbyname(3) and gethostbyaddr(3). Depending on the system's configuration, this resulted in DNS lookups or not, and at least for the cases where not, I needed some other tool to isolate and reproduce an issue using the standard name lookup whatever it was -- DNS, files, or NIS, to name a few.

So I wrote nslook(1). The name as a shortened form of "nslookup" should express what I wanted, a more concise and in some situations more convenient program to look up names and addresses "the normal way", for whatever values of normal your system had.

The program proved to be useful, and while I tinkered with it a bit a few times in the following 20 years, I never made bigger changes. In particular I never made it support the new IPv6 API. I thought about it some times, but was too lazy to go for this change.

End of 2013 I recognized that I needed something exactly like this program again. With that new motivation, I finally made it use the new IPv6 API, which has been present in the relevant platforms for a number of years now. This resulted in some larger changes, but it was still easy to do -- the overall structure of the program was more sound than I had expected from something in my earlier years as a programmer.

Some examples:

$ nslook ribe.w21.org
85.214.199.88
2a01:238:4382:a300:3fe5:41ce:8574:8378

$ nslook -4 ribe.w21.org
85.214.199.88

$ nslook -m ribe.w21.org
85.214.199.88                            ribe.w21.org
2a01:238:4382:a300:3fe5:41ce:8574:8378   ribe.w21.org

$ nslook -l ribe.w21.org
query:      ribe.w21.org
ip address: 85.214.199.88
ip address: 2a01:238:4382:a300:3fe5:41ce:8574:8378

$ nslook -lc mail.w21.org
query:      mail.w21.org
hostname:   ribe.w21.org
ip address: 85.214.199.88
ip address: 2a01:238:4382:a300:3fe5:41ce:8574:8378

$ nslook 85.214.199.88
ribe.w21.org

$ nslook -lr w21.org
query:      w21.org
ip address: 85.214.199.88
reverse:    ribe.w21.org
ip address: 2a01:238:4382:a300:3fe5:41ce:8574:8378
reverse:    ribe.w21.org

If you feel particularly inquisitive, try the -x option with a forward lookup.

The copyright claim and the license conditions in the LICENSE file apply to all files of this package.

In the morgue/ subdirectory you can find a shar file of the program from March 1992 and the original README file. Wow, those were the days...

-- Juergen Nickelsen ni@w21.org 2015-04-13