


Shell arrays and associative arrays
1. Array
1.1. Array definition
A pair of parentheses represents an array, and the array elements are separated by space symbols
xiaosi@Qunar:~$ a=(1 2 3) xiaosi@Qunar:~$ echo $a 1 xiaosi@Qunar:~$ a=("yoona" "lucy" "tom") xiaosi@Qunar:~$ echo $a yoona
1.2. Array length, elements, assignment and deletion
Length: Use ${#array name[@or*]} to get the array length
xiaosi@Qunar:~$ echo ${#a[@]} 3 xiaosi@Qunar:~$ echo ${#a[*]} 3
Get elements: Use ${array name[subscript]} to get the array elements (the subscript starts from 0), and the subscript is * or @ to get the entire array content
xiaosi@Qunar:~$ array=("yoona" "lucy" "tom") xiaosi@Qunar:~$ echo ${array[0]} yoona xiaosi@Qunar:~$ echo ${array[1]} lucy xiaosi@Qunar:~$ echo ${array[*]} yoona lucy tom xiaosi@Qunar:~$ echo ${array[@]} yoona lucy tom
Assignment: Reference assignment can be made through the array name [subscript]. If the subscript does not exist, a new array element will be automatically added
xiaosi@Qunar:~$ array=("yoona" "lucy" "tom") xiaosi@Qunar:~$ echo ${array[2]} tom xiaosi@Qunar:~$ array[2]=lily xiaosi@Qunar:~$ echo ${array[2]} lily
Delete: through unset Array [subscript] can clear the corresponding elements. Without subscript, all data will be cleared.
xiaosi@Qunar:~$ array=("yoona" "lucy" "tom") xiaosi@Qunar:~$ unset array[1] xiaosi@Qunar:~$ echo ${array[*]} yoona tom xiaosi@Qunar:~$ unset array xiaosi@Qunar:~$ echo ${array[*]} xiaosi@Qunar:~$
1.3. Get elements in a certain range
Directly through ${array Name [@ or *]: starting position: length} Get the elements in the given range of the array and return a string, separated by spaces
xiaosi@Qunar:~$ array=(yoona lucy tom) xiaosi@Qunar:~$ echo ${array[*]} yoona lucy tom xiaosi@Qunar:~$ echo ${array[*]:1:2} lucy tom xiaosi@Qunar:~$ echo ${array[@]:0:1} yoona
1.4. Replace
${array name[@ or *]/search character/replace character} This operation will not change the original array content. If you need to modify it, you can see the above example
xiaosi@Qunar:~$ array=(yoona lucy tom) xiaosi@Qunar:~$ echo ${array[@]/lucy/lily} yoona lily tom xiaosi@Qunar:~$ echo ${array[@]} yoona lucy tom
2. Association Array
Bash supports associative arrays, which can use strings as array indexes. Sometimes it is easier to understand using string indexes.
2.1 Define associative array
First you need to use a declaration statement to declare a variable as an associative array.
xiaosi@Qunar:~$ declare -A assArray
After declaration, there are two ways to add elements to an associative array.
(1) Method of using embedded index-value list
xiaosi@Qunar:~$ assArray=([lucy]=beijing [yoona]=shanghai) xiaosi@Qunar:~$ echo ${assArray[lucy]} beijing
(2) Using independent index-value for assignment
xiaosi@Qunar:~$ assArray[lily]=shandong xiaosi@Qunar:~$ assArray[sunny]=xian xiaosi@Qunar:~$ echo ${assArray[sunny]} xian xiaosi@Qunar:~$ echo ${assArray[lily]} shandong
2.2 List array index
Each array has an index for search. Use ${!array name[@or*]} to get the index list of the array
xiaosi@Qunar:~$ echo ${!assArray[*]} lily yoona sunny lucy xiaosi@Qunar:~$ echo ${!assArray[@]} lily yoona sunny lucy
2.3 Get all key-value pairs
#! /bin/bash declare -A cityArray cityArray=([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.sh lily come from shandong yoona come from beijing lucy come from shanghai
Thank you for reading, I hope it can help everyone, thank you everyone for your support of this site!
For more detailed explanations and example codes of Shell arrays and associative arrays, please pay attention to the PHP Chinese website!

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