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Bash Beginner Series #4: Using Arrays in Bash

Arrays to the rescue!

So far, you have used a limited number of variables in your bash script, you have created few variables to hold one or two filenames and usernames.

But what if you need more than few variables in your bash scripts; let’s say you want to create a bash script that reads a hundred different input from a user, are you going to create 100 variables?

Luckily, you don’t need to because arrays offer a much better solution.

Creating your first array in a bash script

Let’s say you want to create a bash script that updates the timestamp of five different files.

First, use the naïve approach of using five different variables:



touch $file1
touch $file2
touch $file3
touch $file4
touch $file5

Now, instead of using five variables to store the value of the five filenames, you create an array that holds all the filenames, here is the general syntax of an array in bash:

array_name=(value1 value2 value3 … )

So now you can create an array named files that stores all the five file names you have used in the script as follows:

files=("f1.txt" "f2.txt" "f3.txt" "f4.txt" "f5.txt")

As you can see, this is much cleaner and more efficient as you have replaced five variables with just one array!

Accessing array elements in bash

The first element of an array starts at index 0 and so to access the nth element of array you use the n -1 index.

For example, to print the value of the 2nd element of your files array, you can use the following echo statement:

echo ${files[1]}

and to print the value of the 3rd element of your files array, you can use:

echo ${files[2]}

and so on.

The following bash script would print out all the five values in your files array in reversed order, starting with the last array element:


files=("f1.txt" "f2.txt" "f3.txt" "f4.txt" "f5.txt")

echo ${files[4]}
echo ${files[3]}
echo ${files[2]}
echo ${files[1]}
echo ${files[0]}

I know you might be wondering why so many echo statement and why don't I use a loop here.

This is because I intend to introduce bash loop concepts later in this series.

You can also print out all the array elements at once:

echo ${files[*]}

f1.txt f2.txt f3.txt f4.txt f5.txt

You can print the total number of the files array elements, i.e. the size of the array:

echo ${#files[@]}


You can also update the value of any element of an array; for example, you can change the value of the first element of the files array to “a.txt” using the following assignment:


Adding array elements in bash

Let’s create an array that contains name of the popular Linux distributions:

distros=("Ubuntu" "Red Hat" "Fedora")

The distros array current contains three elements. You can use the += operator to add (append) an element to the end of the array.

For example, you can append Kali to the distros array as follows:


Now the distros array contains exactly four array elements with Kali being the last element of the array.

Deleting array elements in bash

Let’s first create a num array that will stores the numbers from 1 to 5:

num=(1 2 3 4 5)

You can print all the values in the num array:

echo ${num[*]}

1 2 3 4 5

You can delete the third element of the num array by using the unset shell built-in:

unset num[2]

Now if you print all the values of the num array:

echo ${num[*]}
1 2 4 5

As you can see, the third element of the array num has been deleted.

You can also delete the whole num array in the same way:

unset num

Creating hybrid arrays with different data types

In bash, unlike many other programming languages, you can create an array that contains different data types. Take a look at the following bash script:


user=("john" 122 "sudo,developers" "bash")

echo "User Name: ${user[0]}"
echo "User ID: ${user[1]}"
echo "User Groups: ${user[2]}"
echo "User Shell: ${user[3]}"

Notice the user array contains four elements:

  1. "John" --> String Data Type

  2. 122 --->  Integer Data Type

  3. "sudo,developers" ---> String Data Type

  4. "bash" --->  String Data Type

So, it’s totally ok to store different data types into the same array. Isn't that awesome?

This takes us to the end of this week’s tutorial; I hope you enjoyed it! If you want something more complicated and real-world example, checkout how to split strings in bash using arrays.

Stay tuned for next week as I am going to show you how to use various bash arithmetic operators.

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