Shell script - array definition and getting array elements

Definition of array

Parenthesis ( ) To represent an array , Array elements are separated by spaces

nums=(v1 v2 v3 v4 ... vn)

Be careful , Assignment number = There must be no spaces on either side , It must be next to the array name and the array elements .
Besides , You don't have to assign values to arrays one by one , The following code just assigns values to specific elements ：

ages=([3]=24 [5]=19 [10]=12)

The above code is only for 3、5、10 Element assignment , So the array length is 3.

Get array elements

The following format is generally used ：

${array_name[index]}

n=${nums[2]}  # Said to get  nums  The second element of the array , And then assign it to the variable  n.

echo ${nums[3]}  # Indicative output  nums  The first of an array of  3  Elements .

 Use @ or * You can get all the elements in the array , for example ：
${nums[*]}
${nums[@]}
 Both can get  nums  All elements of the array .

The code is as follows

#!/bin/bash
nums=(29 100 13 8 91 44)
echo ${nums[@]}  # Output all array elements 
nums[10]=66  # Give it to 10 Element assignment （ This will increase the array length ）
echo ${nums[*]}  # Output all array elements 
echo ${nums[4]}  # Output No 4 Elements 

Output ：

29 100 13 8 91 44
29 100 13 8 91 44 66
91

Get array length

utilize @ or *, You can extend arrays to lists , And then use # To get the number of array elements

${#array_name[@]}
${#array_name[*]}

The code is as follows ：

#!/bin/bash
nums=(29 100 13)
echo ${#nums[*]}
# Adding elements to an array 
nums[10]="http://c.biancheng.net/shell/"
echo ${#nums[@]}
echo ${#nums[10]}
# Delete array elements 
unset nums[1]
echo ${#nums[*]}

Output ：

3
4
29
3