In linux, the tab key may be used at most. Using tab when using ls, cd and other commands can help us reduce a lot of keyboard input. For example, if we want to enter a directory with a long directory name, we may only need to type the first few characters, and then use tab. At this time, the entire directory name All have been added. If there are several directories with the same front, it will also prompt, and some systems will make a "beep" sound. If you don't like this sound, you can remove it by modifying the configuration. Edit the /etc/inputrc file with vi to remove it. The # sign in front of "set bell-style none", restart the system!