Re: Obtain hostnames from IP addresses

[David Wright <d.wright@open.ac.uk>]

Quoting Conrado Badenas (Conrado.Badenas@uv.es):
> Does anyone know how to obtain hostnames (e.g., skywalker.termol.uv.es)
> from IP addresses (e.g., 147.156.6.236). I've written this program:
> [...]

>         int l;
>         char addr[]="147.156.6.236";
>         struct hostent *ph;
>         
>         l=strlen(addr);ph=gethostbyaddr(addr,l,AF_INET);

You can do that sort of thing nicely in a language like Python
because it takes care of the structures for you. In C you've got
to do it all yourself. The value of l must be four, and addr
should be a pointer to an in_addr structure in network byte order.

> Is there any program (like a filter: input address in stdin, output name
> in stdout) that could do it? I've tried with nslookup but doesn't work
> (and it worked last month).

nslookup works here today. But I find python ideal for playing around
with these sorts of things. Elegant and easy.

Cheers,

-- 
Email:  d.wright@open.ac.uk   Tel: +44 1908 653 739  Fax: +44 1908 655 151
Snail:  David Wright, Earth Science Dept., Milton Keynes, England, MK7 6AA
Disclaimer:   These addresses are only for reaching me, and do not signify
official stationery. Views expressed here are either my own or plagiarised.