[CALUG] /etc/hosts not used?

[Jeremy Portzer]

On Sat, 18 Mar 2006, Jim Bauer wrote:

> On Saturday 18 March 2006 07:12, Eldon Ziegler wrote:
> > I need a local host name to IP address association to override that
> > provided by DNS. However, after entering the new definition in
> > /etc/hosts the "host" command still returns the IP address from DNS.
> > I've tried in on Linux 2.6 (RedHat ES4) and 2.4 (RedHat 9.x).
> >
> > /etc/host.conf has "order hosts,bind". /etc/nsswitch.conf has "hosts:
> > files dns". Does some service need to be restarted? How do I get
> > /etc/hosts to override DNS?
> 
> I am fairly certain the host command only does DNS lookups.
> So it'll never look in /etc/hosts.
> 
> I think you really want to know what does the gethostbyname() library
> routine will return?  Try this to find out (replacing 'foo' with what
> you want to lookup).
> 
> perl -e '($x) = gethostbyname("foo"); print $x, "\n"'


It's not quite that simple.  gethostbyname() returns a list context with 
several different things, the first argument is the hostname, so the above 
simply returns whatever you give it.  Check the perlfunc and 
gethostbyname() man pages for the full scoop.

Here's a web site that explains how to do this properly in Perl using the 
Socket library:

http://www.unix.org.ua/orelly/perl/cookbook/ch18_02.htm
 
However that doesn't answer the original question of a simple shell 
command to do a hostname lookup using the system resolver library.  It 
seems like there ought to be an easy answer for this, but the only thing I 
can think of is to parse the output of "ping" which can be difficult.

Here's one ugly attempt at this:

ping -n -c 1 foo | head -n 1 | cut -d ' ' -f 3 | sed 's/[()]//g'

If "foo" is an unknown host, ping writes that to standard error, so you 
have to be prepared to handle that too.

--Jeremy

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