Recursive functions in Bash Scripting - Mini Project: Build & Apply

Recursive Functions in Bash

📖 Scenario: You are helping a friend who wants to understand how to use recursion in Bash scripts. Recursion is when a function calls itself to solve smaller parts of a problem. This is useful for tasks like calculating factorials.

🎯 Goal: Build a Bash script that uses a recursive function to calculate the factorial of a given number.

📋 What You'll Learn

Create a Bash function named factorial that calculates factorial recursively

Use a base case to stop recursion when the input is 1

Call the factorial function with a number stored in a variable num

Print the factorial result

💡 Why This Matters

🌍 Real World

Recursive functions help solve problems that can be broken down into smaller similar problems, like file system traversal or mathematical calculations.

💼 Career

Understanding recursion in scripting is useful for automation tasks, system administration, and writing efficient scripts that handle complex data.

1

Set the number to calculate factorial

Create a variable called num and set it to 5.

Bash Scripting

# Create a variable called num and set it to 5
# Your code here

Need a hint?

Use num=5 to set the variable.

2

Write the recursive factorial function

Write a Bash function named factorial that takes one argument n. Use an if statement to check if n is 1. If yes, return 1. Otherwise, return n multiplied by the factorial of n-1.

Bash Scripting

num=5

# Write the factorial function below
# Your code here

Need a hint?

Use if [ "$n" -eq 1 ] for the base case and call factorial $((n - 1)) recursively.

3

Call the factorial function with the number

Call the factorial function with the variable num and save the result in a variable called result.

Bash Scripting

num=5

factorial() {
  local n=$1
  if [ "$n" -eq 1 ]; then
    echo 1
  else
    local prev=$(factorial $((n - 1)))
    echo $((n * prev))
  fi
}

# Call factorial with num and save to result
# Your code here

Need a hint?

Use result=$(factorial "$num") to capture the output.

4

Print the factorial result

Print the text Factorial of 5 is followed by the value of result using echo.

Bash Scripting

num=5

factorial() {
  local n=$1
  if [ "$n" -eq 1 ]; then
    echo 1
  else
    local prev=$(factorial $((n - 1)))
    echo $((n * prev))
  fi
}

result=$(factorial "$num")

# Print the factorial result
# Your code here

Need a hint?

Use echo "Factorial of $num is $result" to print the message.