Indexed array declaration in Bash Scripting - Mini Project: Build & Apply

Indexed array declaration

📖 Scenario: You are organizing a list of your favorite fruits to use in a script that will later process them.

🎯 Goal: Create an indexed array in Bash with specific fruit names, then display the array contents.

📋 What You'll Learn

Create an indexed array named fruits with exact values

Add a variable to hold the number of fruits

Use a loop to print each fruit with its index

Print the total number of fruits at the end

💡 Why This Matters

🌍 Real World

Arrays help organize lists of items like filenames, user inputs, or settings in scripts.

💼 Career

Knowing how to use arrays in Bash is essential for automating tasks and managing data in system administration and DevOps roles.

1

Create the indexed array

Create an indexed array called fruits with these exact values in order: Apple, Banana, Cherry, Date, Elderberry.

Bash Scripting

# Create the indexed array fruits with the given fruits
# Your code here

Hint

Use parentheses () to declare an indexed array in Bash.

2

Add a variable for the number of fruits

Create a variable called count that stores the number of elements in the fruits array.

Bash Scripting

fruits=(Apple Banana Cherry Date Elderberry)
# Create count variable to hold number of fruits
# Your code here

Hint

Use ${#array[@]} to get the length of an array in Bash.

3

Loop through the array and print each fruit

Use a for loop with variable i from 0 to count - 1 to print each fruit with its index in the format: Fruit 0: Apple.

Bash Scripting

fruits=(Apple Banana Cherry Date Elderberry)
count=${#fruits[@]}
# Loop from 0 to count-1 and print each fruit with its index
# Your code here

Hint

Use a C-style for loop in Bash to iterate over array indices.

4

Print the total number of fruits

Print the total number of fruits using the count variable in the format: Total fruits: 5.

Bash Scripting

fruits=(Apple Banana Cherry Date Elderberry)
count=${#fruits[@]}
for ((i=0; i<count; i++)); do
    echo "Fruit $i: ${fruits[i]}"
done
# Print total number of fruits
# Your code here

Hint

Use echo to print the total count variable.

Practice

1. What is the correct way to declare an indexed array named fruits with values apple, banana, and cherry in Bash?

easy

A. fruits=[apple, banana, cherry]

B. fruits=("apple, banana, cherry")

C. fruits={apple banana cherry}

D. fruits=(apple banana cherry)

Solution

1. Step 1: Understand Bash array declaration syntax

   Bash arrays use parentheses with space-separated values, no commas or braces.

2. Step 2: Check each option's syntax

   fruits=(apple banana cherry) uses parentheses and spaces correctly. Square brackets and braces are incorrect. fruits=("apple, banana, cherry") treats all values as one string.

3. Final Answer:

   fruits=(apple banana cherry) -> Option D

4. Quick Check:

   Parentheses + spaces = correct array declaration [OK]

Hint: Use parentheses and spaces, no commas or braces [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Including commas between values
• Putting all values inside quotes as one string

2. Which of the following is the correct syntax to declare an empty indexed array named numbers in Bash?

easy

A. numbers={}

B. numbers=()

C. numbers=[]

D. numbers=""

Solution

1. Step 1: Recall empty array declaration in Bash

   An empty indexed array is declared with empty parentheses.

2. Step 2: Evaluate each option

   numbers=() uses empty parentheses correctly. Braces and square brackets are invalid. numbers="" assigns an empty string, not an array.

3. Final Answer:

   numbers=() -> Option B

4. Quick Check:

   Empty parentheses declare empty array [OK]

Hint: Empty parentheses mean empty array [OK]

Common Mistakes:

• Using square brackets or braces instead of parentheses
• Assigning empty string instead of array
• Confusing array declaration with variable assignment

3. Given the array declaration colors=(red green blue), what will be the output of echo ${colors[1]}?

medium

A. green

B. colors[1]

C. blue

D. red

Solution

1. Step 1: Understand array indexing in Bash

   Indexed arrays start at 0, so index 1 is the second element.

2. Step 2: Identify the element at index 1

   colors[0] = red, colors[1] = green, colors[2] = blue.

3. Final Answer:

   green -> Option A

4. Quick Check:

   Index 1 = second element = green [OK]

Hint: Array indexes start at zero [OK]

Common Mistakes:

• Thinking array starts at 1 instead of 0
• Printing the variable name instead of value
• Confusing index with value

4. What is wrong with this array declaration?

myarray=(one two three four five six seven eight nine ten

medium

A. Array name is invalid

B. Values should be quoted

C. Missing closing parenthesis

D. Values must be comma separated

Solution

1. Step 1: Check array syntax completeness

   The declaration starts with '(' but does not have a closing ')'.

2. Step 2: Verify other syntax rules

   Values do not need quotes if no spaces, array name is valid, commas are not used in Bash arrays.

3. Final Answer:

   Missing closing parenthesis -> Option C

4. Quick Check:

   Parentheses must open and close [OK]

Hint: Always close parentheses in array declaration [OK]

Common Mistakes:

• Forgetting the closing parenthesis
• Adding commas between values
• Quoting values unnecessarily

5. How can you declare an indexed array days with the values Mon, Tue, and Wed, then print the total number of elements in the array?

hard

A. days=(Mon Tue Wed); echo ${#days[@]}

B. days=[Mon Tue Wed]; echo ${#days}

C. days=(Mon, Tue, Wed); echo ${#days[@]}

D. days=(Mon Tue Wed); echo ${days.length}

Solution

1. Step 1: Declare the array correctly

   Use parentheses with space-separated values: days=(Mon Tue Wed).

2. Step 2: Use correct syntax to get array length

   Use ${#days[@]} to get the number of elements in the array.

3. Final Answer:

   days=(Mon Tue Wed); echo ${#days[@]} -> Option A

4. Quick Check:

   Parentheses + ${#array[@]} = count [OK]

Hint: Use ${#array[@]} to get array length [OK]

Common Mistakes:

• Using square brackets for array declaration
• Using commas between values
• Using incorrect syntax for length like ${#days} or .length