Bug of the day: getent's surprise

Your command makes a lot of assumptions. It's unclear what your actual intent really is, here. For example, in my /etc/hosts file, I have:

1.2.3.4 hostname hostname.domain.com

And, "getent hosts hostname" produces that line - it's very similar functionally to "grep '\shostname\s' /etc/hosts".

There's a lot of things to be careful about with your approach ...

Why not use 'host'? I believe that it is likely more portable than 'getent'.

host foo | awk '{print $1}'

Indeed, 'getent' isn't on my workstation at home:

: mac; which getent
: mac; uname -a
Darwin mac.foo.net 12.2.0 Darwin Kernel Version 12.2.0: Sat Aug 25 00:48:52 PDT 2012; root:xnu-2050.18.24~1/RELEASE_X86_64 x86_64
: mac; 

Host's output MAY include multiple lines if there are other DNS RR's for that host (MX records or what not), so piping through tail or doing something like:

host foo | awk '{print $1; exit}'

is probably still advised.

Then again, sometimes things just don't turn out the way I expect:

: well; getent hosts www
10.4.113.126    www.well.com www web.well.com web
: well; host www
Host www not found: 3(NXDOMAIN)
: well; host www.well.com
www.well.com has address 107.20.173.213
: well; 

(I wonder what the output would be if 'www' was listed before 'www.well.com' in the /etc/hosts file?)

Does the hostname command not do this for you in a single command?:

$ hostname --fqdn
gs500.fe.up.pt

"hostname -f" works fine for the host itself but not for looking up other hosts.

IMHO if you're going to use awk then skip the pipe to head otherwise I'd use cut.

echo -e 'foo bar\nbar foo' | awk 'NR==1{print $1}'

But either or, most just pointing it out to make conversation.