//
// at least $threshold full and at the current rate of growth will fill
// the file system in less than $lead_time
// ie. used + $lead_time * growth-rate > capacity

delta = 1 min;		// check every minute
threshold = 40;		// must be at least this full now (percentage)
lead_time = "15min";	// lead time before the filesystem will be full

some_inst (
  100 * filesys.used / filesys.capacity > $threshold &&
  filesys.used + $lead_time * ( rate filesys.used ) >
	filesys.capacity 
) -> print "filesystem will be full within $lead_time:" " %i";