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Understanding Bash history
Speaking of history, let's dive right into that concept. By default, Bash keeps track 
of all the commands you enter during your sessions, so that if you need to recall a 
previously entered command, you can definitely do so. History also serves another 
purpose, and that is seeing what other users have been up to. However, since 
users can edit their own history to cover their tracks, it's not always useful for that 
purpose.
You may have already seen Bash's history feature in some form, if you've ever 
pressed the up and down arrows on the shell to recall a previously used command. 
If you didn't already know you can do that, go ahead and give it a try. You should 
see that by pressing the up and down arrows, you can cycle through commands that 
you've used previously.
Another trick is that you can also simply type 
history
 in the shell and see a list of 
previously entered commands, as shown in 
Figure 6.2
:
Figure 6.2: Output from the history command

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Boosting Your Command-line Efficiency