Append to Bash Array

The array data type is used in bash to store multiple data. The new data can be inserted at the end of an array variable in various ways. Bash has no built-in function like other programming languages to append new data in bash array. How you can insert single and multiple data at the end of the array in bash is shown in this tutorial.

Four different types of examples are shown in this tutorial to append new elements into an array.

Using shorthand operators is the simplest way to append an element at the end of an array. In the following script, an array with 6 elements is declared. Next ‘+=’ shorthand operator is used to insert a new element at the end of the array. ‘for’ loop is used here to iterate the array and print the array elements.

#!/bin/bash

# Declare a string array
arrVar=("AC" "TV" "Mobile" "Fridge" "Oven" "Blender")

# Add new element at the end of the array
arrVar+=("Dish Washer")

# Iterate the loop to read and print each array element
for value in "${arrVar[@]}"
do
     echo $value
done

Another simple way to insert a new element at the end of the array is to define the last index of the array. The index of an array starts from 0, and the total number of elements of the array can find out by using ‘#’ and ‘@’ symbol with the array variable. In the following script, an array variable named ‘arrVar’ is declared that contains four elements. Next, the last index is defined by using ${#arrVar[@]}. A new element is inserted at the end of the array by this last index. The values of the array are printed like the previous example.

#!/bin/bash

# Declare a string array
arrVar=("PHP" "MySQL" "Bash" "Oracle")

# Add new element at the end of the array
arrVar[${#arrVar[@]}]="Python"

# Iterate the loop to read and print each array element
for value in "${arrVar[@]}"
do
     echo $value
done

A new array element can be inserted by using the array variable and the new element value within a first bracket. The following script shows the use of the first brackets to append elements into an array. After appending a new element, the array values are printed by using a loop.

#!/bin/bash

# Declare a string array
arrVar=("Banana" "Mango" "Watermelon" "Grape")

# Add new element at the end of the array
arrVar=(${arrVar[@]} "Jack Fruit")

# Iterate the loop to read and print each array element
for value in "${arrVar[@]}"
do
     echo $value
done

#!/bin/bash

# Declare two string arrays
arrVar1=("John" "Watson" "Micheal" "Lisa")
arrVar2=("Ella" "Mila" "Abir" "Hossain")

# Add the second array at the end of the first array
arrVar=(${arrVar1[@]} ${arrVar2[@]})

# Iterate the loop to read and print each array element
for value in "${arrVar[@]}"
do
     echo $value
done