Nine arrays in the shell

Array: A variable that stores a set of data and is able to manipulate one of the data in this set of data individually.

Types of arrays: one-dimensional arrays, two-dimensional arrays, multidimensional arrays

Types of variables

The default value of an untyped variable in the shell is automatically converted to an integer when it is used as text in a numeric operation.

Defining variable Types

declare: Force set type properties

syntax:declare option variable name

option    Comment -i    Force integer -A    defines an array -X    set to global variable/ environment variable -R    set to read-only

-I: Define variables as numeric types

[Email protected] ~]#declare-i x= ~]# declare-i y=3~]# declare-i c= $x *  ~]# echo $c

-A : Define variable array type

[email protected] ~]# declare-~]# declare-a |  -a tea='()'~]#tea= ~]# declare-a |  -a tea='([0]= "PLJ" [1]= "HPG" [2]= "ZHF" [3]= "Zzg")'

defines or assigns an array of values

Method 1, Overall assignment

format    Example array name = (value 1 value 2 ....) Value N)    svrs= (www ftp mail club)

Method 2: Assign a value to a single element

format    Example array name [subscript]= value; subscript starting    from 0 fqdns[0]=www.tarena.com

Output array elements

    Format gets a single array element    ${array name [subscript]} gets all array elements    ${array name [@]} Gets the number of array elements    ${#数组名 [@]} get successive array elements    ${array name [@]}: Start subscript: The number of elements gets the length of an element of an    array ${#数组名 [subscript]} to intercept part of the value of an element    ${#数组名 [subscript]: Start subscript: Characters}

Special Reminders:

If an element subscript value has already been used by an existing element, the value of the existing element is modified
Adds a new element to an array if the element subscript value is not used by an existing element
If you assign a value to an array, the list of elements is empty, and all elements in the array are deleted
If you assign a value to an array, the element list enters a new value, and it is re-assigned to the array.

Nine arrays in the shell