You can use the TAB key to complete words you are entering on the command line. This facility, called completion, works in both vi and emacs editing modes. Several types of completion are possible, and which one you use depends on which part of a command line you are typing when you press TAB.
If you are typing the name of a command (usually the first word on the command line), pressing TAB initiates command completion, in which bash looks for a command whose name starts with the part of the word you have typed. If no command starts with the characters you entered, bash beeps. If there is one such command, bash completes the command name. If there is more than one choice, bash