. It is extremely helpful when you find yourself in that awkward position where you’ve typed out half of a complex command and know you’re going to need the history to finish the rest. We can do that using the s/original/new/ syntax. To see a certain number of commands, you can pass a number to history on the command line. Since we launched in 2006, our articles have been read more than 1 billion times. command to see their values: PS1 is a primary prompt variable. To use it, type (without spaces) a caret, the text you want to replace, another caret, the text you want to replace it with, another caret, and then press Enter.