Shell

When we speak of the command line, we are really referring to the _shell_. The shell is a program that takes keyboard commands and passes them to the operating system to carry out.

bash

The name is an acronym for _b_ourne-_a_gain _sh_ell, a reference to the fact that bash is an enhanced replacement for sh, the original Unix shell program written by Steve Bourne.

三种 Shell 交互方式

shell prompt

以纯文本形式启动 linux 系统时

Terminal Emulators

When using a graphical user interface (GUI), we need another program called a terminal emulator to interact with the shell.

visual consoles

Even if we have no terminal emulator running, several terminal sessions continue to run behind the graphical desktop. We can access these sessions, called visual consoles , by pressing CTRL-ALT-F1 through CTRL-ALT-F6 on most Linux distributions. To switch from one virtual console to another, press ALT-F1 through ALT-F6. On most systems, we can return to the graphical desktop by pressing ALT-F7.

Ubuntu 20.04 LTS

  • CTRL-ALT-F1 用户选择页面