hostname -- set or print name of current host system

hostname [-fs] [name-of-host]

The hostname utility prints the name of the current host. The super-user can set the hostname by supplying an argument. To keep the hostname between reboots, run scutil --set HostName name-of-host.

-f Include domain information in the printed name. This is the default behavior.
-s Trim off any domain information from the printed name.

gethostname(3), scutil(8)