if {[expr ! [exists -proc pretty_size ]]} {
	proc pretty_size {size} {
		set units {bytes KiB MiB GiB TiB}

		for {set i 0} {$size > 1023} {incr i} {
			set size $($size / 1024.0)
		}

		set size [format "%.2f" $size]

		return "$size [lindex $units $i]"
	}
}