Have you ever executed a command in Unix and noticed the that you had to run it with sudo? Instead of typing the command again with “sudo” in front of it, just run:
$ sudo !!
EDIT (05/06/2011 @ 10:20 PM) Mathew pointed out that running
$ !! command
will put the command at the end of the line. For example
$ rails $ !! server #output $ rails server
!! is a replacement for the previous line entered in the Linux shell.
Update: You can also use !$ for partial replacement. For example
$ mkdir temp_folder_to_delete $ rm -rf !$ #short for rm -rf temp_folder_to_delete