Why does Python 'gethostname()' return the entire FQDN when run on a FreeNAS server console?

Question

I get this (FreeNAS 11.2-RELEASE-U1):

Python 3.6.5 (default, Dec 20 2018, 21:27:40) 
[GCC 4.2.1 Compatible FreeBSD Clang 6.0.0 (tags/RELEASE_600/final 326565)] on freebsd11 
Type "help", "copyright", "credits" or "license" for more information. 
>>> import socket 
>>> print (socket.gethostname()) 
backup-server.example.com
>>>

Wha...?

Answer 1

I think it just returns whatever the underlying gethostname() call does. For example (though this is on Linux):

# hostname foobar
# python -c 'import socket; print(socket.gethostname())'
foobar
# hostname foobar.example.org
# python -c 'import socket; print(socket.gethostname())'
foobar.example.org

If you just want the hostname part, it's not hard to remove the rest:

# python -c 'import socket; import re; print(re.sub("\..*", "", socket.gethostname()))'
foobar

Answer 2

Reading the Python documentation, gethostname doesn't specify what exactly is being returned and FreeBSD contains the FQDN for the machine in the configuration.

Return a string containing the hostname of the machine where the Python interpreter is currently executing.

Note: gethostname() doesn’t always return the fully qualified domain name; use getfqdn() for that.

Other platforms may return only the nodename, but also on Linux this is interesting usecase as the domainname is originally for NIS / Kerberos and doesn't have to match the domainname in DNS.