Shell variables - User variables

1, Shell variables:

(1) command rules: numbers, letters, underscores, first character can not be a number.

Default type (2) are variable string, the value for the type, it must be specified.

(3) case-sensitive, for example: ASD, asd, Asd are different variables.

2, a space for the string should be in double or single quotes:

 

 3, user variables

(1) the definition of variables and see:

 

 (2) variable superposition:

Mode 1:

 

 Option 2:

 

 4, set command:

See all the variables.

 

 5, delete variables

unset + variable names:

 

 variable has no name.