Why doesn't the script show hostname?

Question

linux

Script, returns an empty string instead of hostname

#!/bin/sh
hm=$HOSTNAME
echo $hm

Answer 1

Do you have such a variable in the environment at all?
To begin with, add to the script
printenv
. In general, to begin with, type hostname or cat /etc/hostname in the console, perhaps the script is doing everything right.

Answer 2

Perhaps everything is simpler and he was trying to simply declare this variable
hm=$(hostname); echo $hm