Operator of Shell programming

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

-: Set the type attribute to the variable +: cancels the Type property of the variable

-A: Declaring variables as arrays-I: declaring variables as integers

-x: Declaring a variable as an environment variable-r: Declaring a variable as a read-only variable

-P: Displays the declared type of the specified variable

Method of numerical operation: Aa=1 bb=2 cc=$ (($aa + $bb))

Operator of Shell programming