Shell array and associated array details and instance code

This article mainly introduces the Shell array and associated array details and information about the instance code. For more information, see Shell array and associated array.

1. array

1.1. array definition

An array is represented by parentheses, and elements in the array are separated by spaces.

xiaosi@Qunar:~$ a=(1 2 3)xiaosi@Qunar:~$ echo $a1xiaosi@Qunar:~$ a=("yoona" "lucy" "tom")xiaosi@Qunar:~$ echo $ayoona

1.2. array length, element, value assignment and deletion

Length: use $ {# array name [@ or *]} to obtain the array length.

xiaosi@Qunar:~$ echo ${#a[@]}3xiaosi@Qunar:~$ echo ${#a[*]}3

Get element: use $ {array name [subscript]} to get the array element (subscript starts from 0), subscript is * or @ to get the entire array content

xiaosi@Qunar:~$ array=("yoona" "lucy" "tom")xiaosi@Qunar:~$ echo ${array[0]}yoonaxiaosi@Qunar:~$ echo ${array[1]}lucyxiaosi@Qunar:~$ echo ${array[*]}yoona lucy tomxiaosi@Qunar:~$ echo ${array[@]}yoona lucy tom

Assign value: the array name [subscript] can be used to reference and assign values. if the subscript does not exist, a new array element is automatically added.

xiaosi@Qunar:~$ array=("yoona" "lucy" "tom")xiaosi@Qunar:~$ echo ${array[2]}tomxiaosi@Qunar:~$ array[2]=lilyxiaosi@Qunar:~$ echo ${array[2]}lily

Delete: The unset array [subscript] can be used to clear the corresponding elements. all data is cleared without a subscript.

xiaosi@Qunar:~$ array=("yoona" "lucy" "tom")xiaosi@Qunar:~$ unset array[1]xiaosi@Qunar:~$ echo ${array[*]}yoona tomxiaosi@Qunar:~$ unset arrayxiaosi@Qunar:~$ echo ${array[*]}xiaosi@Qunar:~$

1.3. obtain elements in a certain range

Use $ {array name [@ or *]: start position: length} to obtain elements in the specified range of the array. return strings separated by spaces.

xiaosi@Qunar:~$ array=(yoona lucy tom)xiaosi@Qunar:~$ echo ${array[*]}yoona lucy tomxiaosi@Qunar:~$ echo ${array[*]:1:2}lucy tomxiaosi@Qunar:~$ echo ${array[@]:0:1}yoona

1.4. replace

$ {Array name [@ or *]/find character/replace character} this operation does not change the original array content. if you need to modify it, refer to the above example.

xiaosi@Qunar:~$ array=(yoona lucy tom)xiaosi@Qunar:~$ echo ${array[@]/lucy/lily}yoona lily tomxiaosi@Qunar:~$ echo ${array[@]}yoona lucy tom

2. join an array

Bash supports associating arrays. it can use strings as array indexes. sometimes it is easier to understand using string indexes.

2.1 define correlated arrays

First, declare a variable as an associated array using the declaration statement.

xiaosi@Qunar:~$ declare -A assArray

After the element is declared, you can add the element to the joined array in two ways.

(1) using the embedded index-value list method

xiaosi@Qunar:~$ assArray=([lucy]=beijing [yoona]=shanghai)xiaosi@Qunar:~$ echo ${assArray[lucy]}beijing

(2) assign values using independent index-values

xiaosi@Qunar:~$ assArray[lily]=shandongxiaosi@Qunar:~$ assArray[sunny]=xianxiaosi@Qunar:~$ echo ${assArray[sunny]}xianxiaosi@Qunar:~$ echo ${assArray[lily]}shandong

2.2 List array indexes

Each array has an index for search. Use $ {! Array name [@ or *]} to obtain the index list of the array

xiaosi@Qunar:~$ echo ${!assArray[*]}lily yoona sunny lucyxiaosi@Qunar:~$ echo ${!assArray[@]}lily yoona sunny lucy

2.3 obtain all key-value pairs

#! /bin/bashdeclare -A cityArraycityArray=([yoona]=beijing [lucy]=shanghai [lily]=shandong)for key in ${!cityArray[*]}do echo "${key} come from ${cityArray[$key]}"done

Result:

xiaosi@Qunar:~/company/sh$ bash array.shlily come from shandongyoona come from beijinglucy come from shanghai

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