Bash Arrays - The Lazy Admin Blog

Bash arrays are used to store multiple values in a single variable.
Here’s a guide with examples on how to use arrays in Bash.

Declaring an Array

To declare an array in Bash, you can use the following syntax:

# Method 1: Using parentheses with space-separated values
my_array=(value1 value2 value3)
 
# Method 2: Using individual assignments
my_array[0]=value1
my_array[1]=value2
my_array[2]=value3

Accessing Array Elements

To access a specific element in the array, use the index of the element:

echo ${my_array[0]}  # Output: value1
echo ${my_array[1]}  # Output: value2

Array Length

To find the length of the array, use the ${#array[@]} syntax:

echo ${#my_array[@]}  # Output: Number of elements in the array

Iterating through an Array

You can loop through the elements of an array using a for loop:

# Iterate through the array elements
for item in "${my_array[@]}"
do
    echo $item
done

Adding Elements to an Array

To add elements to an array, you can use various methods:

# Method 1: Append elements using parentheses
my_array+=(value4 value5)
 
# Method 2: Assign a value to a specific index
my_array[3]=value4
my_array[4]=value5

Removing Elements from an Array

To remove elements from an array, you can unset specific indexes:

unset my_array[2]  # Removes the element at index 2

Example

Here is an example that should help you understand how to use arrays in Bash and perform various operations on them.

# Declare an array
fruits=(Apple Orange Banana)
 
# Access elements
echo "First fruit: ${fruits[0]}"  # Output: Apple
echo "Number of fruits: ${#fruits[@]}"  # Output: Number of elements
 
# Loop through the array elements
for fruit in "${fruits[@]}"
do
    echo "Fruit: $fruit"
done
 
# Add elements to the array
fruits+=(Grapes)
fruits[3]="Pineapple"
 
# Remove an element
unset fruits[1]  # Removes 'Orange'
 
# Print the updated array
echo "Updated array:"
for fruit in "${fruits[@]}"
do
    echo "Fruit: $fruit"
done

Tags: bash