Shell variable operation

1. Define variables: In order to avoid conflicts with environment variables, generally lowercase: such as pp= "mydql,kdkfeof";

Second assignment scheme:

The calling variable uses the $ symbol:

Variable overlay:

2. The output uses ECHO, as shown in:

3. Variable classification: Custom variables and environment variables.

4. View: Set, view all variables and their values

5. Delete variable: unset variable name, such as:

　

6. Scope of Action:

The custom variable only acts on the current shell. Once the current terminal is closed, it loses its function.

7. Environment variable declaration: Export variable name = value. View: Env.

Shell variable operation