"Bash's command history can be referenced using the exclamation mark. For instance, typing two exclamation marks (!!) will re-execute the last command. The next example executes date twice:
"date
!!
"If you are interested in more than just the last command executed, type history to see a numbered listing of your Bash's history.
"history
39 grep root /etc/passwd
40 date
41 date
42 history"
