Shell array

You can store multiple values in an array .Bash Shell Only one-dimensional arrays are supported （ Multidimensional arrays are not supported ）, There is no need to define the array size when initializing （ And PHP similar ）. Similar to most programming languages , The subscripts of array elements are 0 Start .

Create array

Shell Arrays are represented in parentheses , Element use ” Space ” Symbol split , The syntax is as follows ： array_name=(value1 value2 ... valuen) example

1. #!/bin/bash
2. my_array=(A B "C" D)
3. We can also use subscripts to define arrays :
4. array_name[0]=value0
5. array_name[1]=value1
6. array_name[2]=value2

Read array

The general format for reading array element values is ： ${array_name[index]}

1. example
2. #!/bin/bash
3. my_array=(A B "C" D)
4. echo " The first element is : ${my_array[0]}"
5. echo " The second element is : ${my_array[1]}"
6. echo " The third element is : ${my_array[2]}"
7. echo " The fourth element is : ${my_array[3]}"

Execute the script , The output is as follows ：

1. $ chmod +x test.sh
2. $ ./test.sh
3. The first element is : A
4. The second element is : B
5. The third element is : C
6. The fourth element is : D

Get all the elements in the array

Use @ or * You can get all the elements in the array for example ：

1. #!/bin/bash
2. my_array[0]=A
3. my_array[1]=B
4. my_array[2]=C
5. my_array[3]=D
6. echo " The elements of the array are : ${my_array[*]}"
7. echo " The elements of the array are : ${my_array[@]}"

Execute the script , The output is as follows ：

1. $ chmod +x test.sh
2. $ ./test.sh
3. The elements of the array are : A B C D
4. The elements of the array are : A B C D

Gets the length of the array

The way to get the array length is the same as the way to get the string length for example ：

1. #!/bin/bash
2. my_array[0]=A
3. my_array[1]=B
4. my_array[2]=C
5. my_array[3]=D
6. echo " The number of array elements is : ${#my_array[*]}"
7. echo " The number of array elements is : ${#my_array[@]}"

Execute the script , The output is as follows ：

1. $ chmod +x test.sh
2. $ ./test.sh
3. The number of array elements is :4
4. The number of array elements is :4