Mac OS X doesn’t let you know how much MB of stuff there are in the trash, before you empty it: is there a way to do with AppleScript?
This will do the job:
(size of (info for (path to trash))) / (1024 ^ 2)
set trashMB to text 1 thru 4 of ((result as text) & "0000")
set numItems to ((do shell script "find ~/.Trash | wc -l") as number) - 1
display dialog "Empty trash? (" & trashMB & " MB for " & numItems & " items)" with icon note
tell application "Finder" to empty
For volumes’ trashes, follow this link:
http://bbs.applescript.net/viewtopic.php?t=3566
It works very well, many thanks!