Count of Unique Hosts in Linux

The following splunk query example will return a unique count of hosts in a given time range *NOTE* if the host field is being autoextracted (for instance if you are using a universal forwarder) you will not need the regex command and can call upon the auto extracted fieldname of "host"

sourcetype=linux_secure |rex ".*:\d{2}\s(?<hostname>\S+)" | stats dc(hostname)