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Arrays in Bash Shell

 

Creating and Using Arrays in Bash Shell Script

In Bash scripting, arrays are used to store multiple values in a single variable. Here's a step-by-step beginner-friendly explanation of how to create and use arrays.

1. Declaring an Array

You can create an array by assigning values to it using parentheses () and separating the values with spaces.

Example:

my_array=(apple banana cherry)

Here:

  • my_array is the name of the array.
  • It stores three elements: "apple", "banana", and "cherry".

2. Accessing Array Elements

Array elements are accessed using their index, starting from 0. You use the syntax ${array_name[index]} to access an element.

Example:

echo ${my_array[0]}  # Outputs: apple
echo ${my_array[1]}  # Outputs: banana
echo ${my_array[2]}  # Outputs: cherry

3. Adding Elements to an Array

You can add a new element by assigning a value to a specific index.

Example:

my_array[3]="date"
echo ${my_array[3]}  # Outputs: date

4. Displaying All Elements

To display all elements of the array, use @ or * inside the curly braces.

Example:

echo ${my_array[@]}  # Outputs: apple banana cherry date
echo ${my_array[*]}  # Outputs: apple banana cherry date

5. Finding the Length of an Array

You can find the number of elements in the array using the syntax ${#array_name[@]}.

Example:

echo ${#my_array[@]}  # Outputs: 4

6. Looping Through an Array

You can use a for loop to iterate over all elements in an array.

Example:

for item in "${my_array[@]}"; do
  echo $item
done

Output:

apple
banana
cherry
date

7. Removing an Element

To remove an element, use the unset command followed by the array name and index.

Example:

unset my_array[1]
echo ${my_array[@]}  # Outputs: apple cherry date

8. Replacing an Element

You can update the value of a specific index.

Example:

my_array[1]="blueberry"
echo ${my_array[@]}  # Outputs: apple blueberry cherry date

9. Examples in Action

Here’s a complete script that demonstrates creating and using arrays:

Script:

#!/bin/bash

# Create an array
fruits=("apple" "banana" "cherry")

# Access elements
echo "First fruit: ${fruits[0]}"

# Add an element
fruits[3]="date"

# Display all elements
echo "All fruits: ${fruits[@]}"

# Find the length of the array
echo "Number of fruits: ${#fruits[@]}"

# Loop through the array
echo "Fruits list:"
for fruit in "${fruits[@]}"; do
  echo $fruit
done

# Remove an element
unset fruits[1]
echo "After removal: ${fruits[@]}"

# Replace an element
fruits[1]="blueberry"
echo "After replacement: ${fruits[@]}"

Key Points to Remember
  • Array indices start at 0.
  • Use ${array_name[index]} to access individual elements.
  • Use "${array_name[@]}" to access all elements.
  • Use ${#array_name[@]} to find the number of elements.

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