Summary of Creating and Using Array Methods in Bash Scripts

Defining an array in Bash

There are two ways to create new arrays in bash scripts. The first is to use the declare command to define an Array. This command will define an associative array named test_array.

$ declare -a test_array

Arrays can also be created by assigning elements.

$ test_array=(apple orange lemon)

Accessing array elements

Similar to other programming languages, bash array elements can be accessed using index numbers starting from 0 and then 1, 2, 3, ... n. This also works for associative arrays where the index numbers are numeric.

$ echo ${test_array[0]}

apple

Use @ or * instead of a specific index number to print all elements of an array.

$ echo ${test_array[@]}

apple orange lemon

Looping through an array

You can also access array elements using loops in bash scripting. Loops are very useful to go through all the array elements one by one and perform some operation on them.

for i in ${test_array[@]}

do

echo $i

don

Adding new elements to an array

You can use the (+=) operator to add any number of elements to an existing array. Just 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 array elements, just assign any new value to the existing array by index. Let's change the current array element at index 2 with grapes.

$ test_array[2]=grapes

View array elements after adding a new element:

$ echo ${test_array[@]}

apple orange grapes mango banana

Deleting an array element

Any array element can be simply deleted using its index number. Following is to remove the element at index 2 from an array in bash script.

$ unset test_array [2]

View array elements after adding a new element:

$ echo ${test_array[@]}

apple orange mango banana