Operator of Shell programming

1. Weaknesses of Shell variables: weak type and default string type

2. Declare command

2.1 Declare declaring variable type declare [+/-] [option] Variable name

　　　　

2.1.1 Declares a numeric type variable: declare-i c= $a + $b # A and B are not declared or can be

2.1.2 declaring an array variable:

　　　　　　

2.1.3 Declaring environment variables: Declare-x a=123 # is similar to export, but it's all part of the DECLARE command.

2.1.4 Declaration Variable read-only property: Declare-r a=123 # Cannot modify delete cancel (NO)

2.1.5 Properties of the query variable: DECLARE-P # Querying properties of all variables

Declare-p Variable name # Querying the properties of a specified variable

3. Method of numerical operation

3.1 Method of Operation:

　　　　

　　　　

　　　　

3.2 Operators:

　　　　

Example:

　　　　

4. Variable test (used when scripting is optimized)

　　

　　

　　

Operator of Shell programming