1.2 Shell variables

#系统变量

Env View System Variables

echo $HOSTNAME View variable contents

Set view system environment variables, also display user-defined variables, compare all

#用户自定义变量

a=1;b=2 Defining variables

echo $a $b output variable value

#引用变量执行结果

Myvim= ' which vim '

#变量与数字相结合要加双引号

D= "$myvim" 3

#进入子shell, the previously defined variable does not exist

Bash

#要使用之前定义的变量, to declare globally

Export A=1

Bash

The variables defined before the Echo $a can also be used

#取消变量值

Unset D

Echo $d

Exercises

1. What are the rules that a variable name needs to conform to when customizing variables?

Variable names can contain uppercase letters

Variable names can only contain numbers, letters, and underscores

2. Which command can I use to display the variables you just defined?

Set

3. What do I need to do if I want to use a custom variable in a child shell?

Export A=1

Summarize:

Main: Global declaration variable export cancel variable value unset

1.2 Shell variables