Operator of Shell programming

Source: Internet
Author: User

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

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