An array is a data structure consist multiple elements based on key pair basis. Each array element is accessible via a key index number.
This tutorial will help you to create an Array in bash script. Also, initialize an array, add an element, update element and delete an element in the bash script.
Define An Array in Bash
You have two ways to create a new array in bash script. The first one is to use declare command to define an Array. This command will define an associative array named test_array.
declare -a test_array
In another way, you can simply create Array by assigning elements.
test_array=(apple orange lemon)
Access Array Elements
Similar to other programming languages, Bash array elements can be accessed using index number starts from 0 then 1,2,3…n. This will work with the associative array which index numbers are numeric.
echo ${test_array[0]} apple
To print all elements of an Array using @ or * instead of the specific index number.
echo ${test_array[@]} apple orange lemon
Loop through an Array
You can also access the Array elements using the loop in the bash script. A loop is useful for traversing to all array elements one by one and perform some operations on it.
1 2 3 4 | for i in ${test_array[@]} do echo $i done |
Adding New Elements to Array
You can add any number of more elements to existing array using (+=) operating. You just need to add new elements like:
test_array+=(mango banana)
View the array elements after adding new:
echo ${test_array[@]} apple orange lemon mango banana
Update Array Elements
To update the array element, simply assign any new value to the existing array by the index. Let’s change the current array element at index 2 with grapes.
test_array[2]=grapes
View the array elements after adding new:
echo ${test_array[@]} apple orange grapes mango banana
Delete An Array Element
You can simply remove any array elements by using the index number. To remove an element at index 2 from an array in bash script.
unset test_array[2]
View the array elements after adding new:
echo ${test_array[@]} apple orange mango banana
6 Comments
I am seeing lots of webpages showing how to operate ARRAYS on Bash with Strings but… how to operate them with NUMBER?
And (worst) how to POPULATE then with these numbers from it being initially EMPTY?
And (once more worst) how to populate them with variables that carry numbers (not strings)?
declare -a array=( $(for i in {1..10}; do echo 0; done) ) # empty array
j=0
for i in ${array[@]}
do
echo $i
done
# numbered array
for i in ${array[@]}
do
array[j]=$j
j=$((j+1))
done
for i in ${array[@]}
do
echo $i
done
Hi, how do I add “green apple” to this array?
Hi, You can use following syntax:
test_array=(“green apple” orange lemon)
Loop through an Array, typo instead of `don` should be `done`
Thanks Mike, Article has been updated correctly.