Shell array

1 Introduce

Shell Support array （Array）, An array is a collection of data , Each piece of data is called an element of an array . Only one-dimensional arrays are supported , Multidimensional arrays are not supported .

2 grammar

stay Shell in , Parenthesis ( ) To represent an array , Array elements are separated by spaces . The grammar is ：

array_name=(item1  item2 ...)  #  The way 1
array_name=([ Index subscript 1]=item1  [ Index subscript 2]=item2  ...)  #  The way 2

3 Get array

1 Get the element value by subscript ,index from 0 Start

${arr[index]}

2 . Get the value and copy it to other variables

item=${arr[index]}

3 Use @ or * You can get all the elements in the array

${arr[@]}
${arr[*]}

4 Get the length or number of arrays

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

5 Gets the character length of the specified element of the array

${#arr[ Indexes ]}

demo:

#!/bin/bash
array=(1 2 3 4 5 6 "hello world" 38)


echo "array All elements are : ${array[*]}"
echo "array The length is : ${#array[*]}"


echo "index Subscript to be 0 Value : ${array[0]}"
echo "index Subscript to be 6 Value : ${array[6]}"

echo "index Subscript to be 6 The length of the string is ：${#array[6]}"

4 Array splicing

4.1 Introduce

So-called Shell Array splicing （ Array merge ）, Is to join two arrays into an array

4.2 grammar

Use @ and * Get all the elements of the array and splice them

array_new=(${array1[@]} ${array2[@]} ...)
array_new=(${array1[*]} ${array2[*]} ...)

4.3 demonstration

#!/bin/bash
array1=(1 2 3)
array2=(4 5 6)

array3=(${
    array1[*]} ${
    array2[*]})


echo "array3  The length of the array : ${#array3[*]}"
echo "array3  All elements : ${array3[*]}"

5 Array deletion

5.1 Introduce

Delete array specifies the element data and deletes the entire array data

5.2 grammar

# Delete array specified element data 
unset array_name[index]

# Delete the entire array 
unset array_name

5.3 demo

#!/bin/bash
array1=(1 2 3)
array2=(4 5 6)


echo "array1: ${array1[*]}"
echo " Delete array array1"
unset array1
echo "array1: ${array1[*]}"


echo "array2: ${array2[*]}"
echo " Delete array1 Subscript to be 0 The elements of "
unset array2[0]
echo " After deleting  array1: ${array2[*]}"