The general function of Linux and the introduction of Shell

1. Common functions in the Linux character interface

1. Tab
2. Up and down cursor keys

2. The concept and type of Shell and the execution process of commands

Shell其实是个软件或者说是一个程序文件。Linux当前使用的Shell通过命令# echo $SHELL查看是：/bin/bash。

3. The general format of the command

1. 
2. 

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