Bash history expansion allows you to quickly re-run previous commands using ! and the number of the command in your history.
You can adjust the size of the history by setting the HISTSIZE variable in the shell e.g.
export HISTSIZE=1000. You can clear the current history with
Bash keeps a history of all commands executed in the shell and this can be referenced using the
! command. Typing two !'s at the prompt will execute the previous command:
$ echo "HELLO" HELLO $ !! echo "HELLO" HELLO
The history of the bash shell can be accessed by entering
501 echo "HELLO" 502 echo "HELLO" 503 history
Notice that each entry has an associated number which can be used to refer to the command.
Entering ! followed by a line number from the history will run that command
$ !501 echo "HELLO" HELLO
You can also search the history by using a search string to match the command instead of a number
$ !echo echo "HELLO" HELLO
This method is based, with permission, on an original protocol available here.