Why conditionals branch script logic in Bash Scripting - See It in Action

Why conditionals branch script logic

📖 Scenario: You are writing a simple script to check if a folder exists on your computer. Depending on whether the folder is there or not, the script will print a different message. This helps you understand how conditionals can change what your script does.

🎯 Goal: Build a bash script that uses a conditional if statement to check if a folder named my_folder exists. If it exists, print Folder exists. If it does not exist, print Folder does not exist.

📋 What You'll Learn

Create a variable called folder with the value my_folder

Create a variable called exists_message with the value Folder exists

Create a variable called not_exists_message with the value Folder does not exist

Use an if statement with the test [ -d "$folder" ] to check if the folder exists

Print $exists_message if the folder exists

Print $not_exists_message if the folder does not exist

💡 Why This Matters

🌍 Real World

Scripts often need to check if files or folders exist before doing tasks like backups or installations.

💼 Career

Understanding conditionals is essential for automation, system administration, and writing reliable scripts.

1

Set up folder and message variables

Create a variable called folder and set it to my_folder. Then create two variables: exists_message with the value Folder exists and not_exists_message with the value Folder does not exist.

Bash Scripting

# Create the variables folder, exists_message, and not_exists_message
# Your code here

Need a hint?

Use the syntax variable_name="value" to create variables in bash.

2

Write the if condition to check folder existence

Write an if statement that uses [ -d "$folder" ] to check if the folder exists. Inside the if, add a comment # Folder exists. After the if, add an else with a comment # Folder does not exist.

Bash Scripting

folder="my_folder"
exists_message="Folder exists"
not_exists_message="Folder does not exist"

# Write if condition to check if folder exists
# Your code here

Need a hint?

Use if [ condition ]; then ... else ... fi to write conditionals in bash.

3

Add commands to print messages inside the if and else blocks

Inside the if block, add a command to print $exists_message. Inside the else block, add a command to print $not_exists_message.

Bash Scripting

folder="my_folder"
exists_message="Folder exists"
not_exists_message="Folder does not exist"

if [ -d "$folder" ]; then
    # Print exists_message
    # Your code here
else
    # Print not_exists_message
    # Your code here
fi

Need a hint?

Use echo "$variable_name" to print the value of a variable in bash.

4

Run the script and see the output

Run the script and observe the output. The script should print Folder exists if the folder my_folder exists, or Folder does not exist if it does not.

Bash Scripting

folder="my_folder"
exists_message="Folder exists"
not_exists_message="Folder does not exist"

if [ -d "$folder" ]; then
    echo "$exists_message"
else
    echo "$not_exists_message"
fi

# Run the script to see the output

Need a hint?

Use bash script_name.sh to run your script in the terminal. The output depends on whether the folder my_folder exists.