Bash Array

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Bash Array

It can be define as the collections of a similar type of elements.In bash, There are no option for multi-dimensional arrays but yes bash provide the support of one-dimensional numerically indexed arrays.

Initialization

To initialize a array in bash, we use assignment operator (=), by specifying the list of the elements within parentheses and separated by spaces like below:

 ARRAY_NAME=(element_1st element_2nd-------- element_Nth)

Access Elements

echo ${ARRAY_NAME[2]}

Operations

Once an array is initialized, we can perform many useful operations on it. We can display its keys and values as well as modify it by appending or removing the elements and many more:

Reference Elements

To reference a single element of a array, we should know the index value of the element. We can print any element using the following syntax:

${ARRAY_NAME[index]}

Example –

#!/bin/bash
#Script to print an element of an array with an index of 1

#Declaring the array
array1=( "Welcome""To""Shell" )

#printing the element with index of 1
echo ${array[1]}


--Output--

TO

Printing the Keys

We can print the keys used in indexed, instead of their respective values. It can be performed by adding the “!” operator before the name as below:

Syntax — {!ARRAY_NAME[index]}

Example

#!/bin/bash
#Script to print the keys of the array

#Declaring the Array
array2=( "Welcome""To""Shell" )

#Printing the Keys
echo "${!array[@]}" 

---Output---

0  1  2

Finding Length

We can count the number of elements contained as below..

Syntax– ${#ARRAY_NAME[@]}

Example

#!/bin/bash  

### Declaring the Array  
array3=( "Welcome""TO""the""Knoldus""Noida")

### Printing Array Length  
echo "The array contains ${#array3@]} elements" 

---Output---

The array contains 5 elements

Adding Elements

We can add elements to an indexed in array by specifying their index. To add the new element in bash, we can use the following form:

Syntax — ARRAY_NAME[index_n]=”New Element”

Example

#!/bin/bash

#Declaring an array
array=( "Kotlin""Python""PHP""HTML""Ruby" )

#Adding new element
array[4]="JavaScript"

#Printing all the elements
echo "${array[@]}" 

--- Output---

Java Python PHP HTML JavaScript

Updating Element

We have a option to update the element by assigning a new value to the existing array by its index value. Let’s change the element at index 4 with an element ‘Knoldus Blog’.

Example

#!/bin/bash
#Script to update array element

#Declaring the array
array=( "We""welcome""you""on")

#Updating the Array Element
array[4]=Knoldus Blog

#Printig all the elements of the Array
echo ${array[@]} 

--- Output---

We welcome you on Knoldus Blog

Deleting an Element

If we want to delete the element, we have to know its index or key in case of an associative array. An element can be removed by using the ‘unset’ command:

Syntax– unset ARRAY_NAME[index]

Example–

#!/bin/bash
#Script to delete the element from the array

#Declaring the array
array=( "Java""Python""HTML""CSS""JavaScript" )

#Removing the element
unset array[1]

#Printing all the elements after deletion
echo "${array[@]}" 

### Output

Java HTML CSS JavaScript