Yes, it should be followed by the filename. Pressing control-c would have worked to stop the command too. I see the locate command returned nothing.
Example of another way, since this is more sure to work:
Command: sudo nextcloud.occ config:system:get datadirectory
Returns: /var/www/nextcloud/data
Add /nextcloud.log to get the command
Command: tail /var/www/nextcloud/data/nextcloud.log