Shell simple use one of the variables (v)

About variables

1. Defining and displaying variables

There are spaces, special characters, etc.

　　

2. Defining and displaying variables

Single quote action and cancellation settings

　　

3. Command-in-order

　　

Two commands to achieve the same effect

4. Environment variables

5. All variables

　　

6. Export custom variables into variables that are available to child processes. Can be called environment variable

7. Current PID and last command return value

　　

8. Language variables

Currently supported languages

　　

Current settings

　　

Shell simple use one of the variables (v)