The ‘GREP’ is a command line search utility or tool to filter the input given to it. The ‘Grep’ got it’s name from ed editor as g/re/p (global / regular expression / print). It can improve a command output by filtering out the required information. The ‘Grep’ will become a killer command when we combine it with regular expressions. The ‘grep -i’ command is used to find the specific word. It is a case insensitive. We can type in lowercase, uppercase or a mix of both.