What a shell script is in Bash Scripting - Mini Project: Build & Apply

What a shell script is

📖 Scenario: Imagine you want to tell your computer to do a few simple tasks automatically, like saying hello and showing the date. Instead of typing commands one by one, you can write them down in a file and run it all at once. This file is called a shell script.

🎯 Goal: You will create a simple shell script that prints a greeting and shows the current date.

📋 What You'll Learn

Create a shell script file with the correct first line (shebang).

Write commands inside the script to print a greeting message.

Write a command to display the current date.

Run the script to see the output.

💡 Why This Matters

🌍 Real World

Shell scripts help automate repetitive tasks on your computer, saving time and effort.

💼 Career

Knowing how to write and run shell scripts is useful for system administrators, developers, and anyone working with computers.

1

Create the shell script file with shebang

Create a file named greet.sh and add the first line #!/bin/bash to tell the computer this is a shell script.

Bash Scripting

# Your code here

Hint

The first line #!/bin/bash tells the system to use the bash shell to run the script.

2

Add a greeting message

Add a line to the greet.sh script that prints Hello, friend! using the echo command.

Bash Scripting

#!/bin/bash
# Your code here

Hint

Use echo followed by the message in quotes to print text.

3

Add a command to show the current date

Add a line to the greet.sh script that runs the date command to show the current date and time.

Bash Scripting

#!/bin/bash
echo "Hello, friend!"
# Your code here

Hint

The date command shows the current date and time.

4

Run the shell script and see the output

Run the greet.sh script in the terminal using bash greet.sh and observe the output.

Bash Scripting

#!/bin/bash
echo "Hello, friend!"
date
# Run the script in terminal

Hint

Use the command bash greet.sh to run your script and see the greeting and date printed.

Practice

1. What is a shell script in simple terms?

easy

A. A file containing commands that run automatically in the shell

B. A program that only runs on Windows

C. A type of hardware device

D. A graphical user interface for the computer

Solution

1. Step 1: Understand what a shell script is

   A shell script is a text file with commands that the shell can run automatically.

2. Step 2: Compare options to definition

   Only A file containing commands that run automatically in the shell describes a file with commands running automatically in the shell.

3. Final Answer:

   A file containing commands that run automatically in the shell -> Option A

4. Quick Check:

   Shell script = file with commands [OK]

Hint: Think: script means commands saved to run later [OK]

Common Mistakes:

• Confusing shell script with software programs
• Thinking shell scripts are hardware
• Believing shell scripts are graphical tools

2. Which of these is the correct way to start a shell script file?

easy

A.

B. #!/bin/bash

C. print('Hello World')

D. function main() {}

Solution

1. Step 1: Identify the shell script shebang

   The first line in a shell script usually starts with #!/bin/bash to tell the system to use bash shell.

2. Step 2: Check other options

   <!DOCTYPE html> is for HTML, print('Hello World') is Python, function main() {} is like JavaScript. None are shell script shebangs.

3. Final Answer:

   #!/bin/bash -> Option B

4. Quick Check:

   Shell scripts start with #!/bin/bash [OK]

Hint: Look for #! to start shell scripts [OK]

Common Mistakes:

• Using code from other languages as shell script start
• Omitting the shebang line
• Confusing shell script with HTML or Python

3. What will this shell script output?

#!/bin/bash
echo "Hello, World!"

medium

A. Error: command not found

B. echo "Hello, World!"

C. No output

D. Hello, World!

Solution

1. Step 1: Understand the echo command

   The echo command prints the text inside quotes to the screen.

2. Step 2: Predict the output

   The script will print exactly: Hello, World!

3. Final Answer:

   Hello, World! -> Option D

4. Quick Check:

   echo prints text = Hello, World! [OK]

Hint: echo prints text exactly as given [OK]

Common Mistakes:

• Thinking echo prints the command itself
• Expecting error without cause
• Assuming no output without running script

4. This shell script is supposed to print "Done" but it shows an error:

#!/bin/bash
echo Done

What is the likely problem?

medium

A. The shebang line is incorrect

B. The echo command is misspelled

C. The script file is missing execute permission

D. The script needs a semicolon after echo

Solution

1. Step 1: Check script permissions

   If the script shows an error when run, it might not have execute permission set.

2. Step 2: Verify other options

   Echo is correct, shebang is correct, and semicolon is not needed after echo.

3. Final Answer:

   The script file is missing execute permission -> Option C

4. Quick Check:

   Missing execute permission causes errors [OK]

Hint: Make script executable with chmod +x [OK]

Common Mistakes:

• Assuming syntax error without checking permissions
• Adding unnecessary semicolons
• Changing correct shebang line

5. You want to automate cleaning temporary files daily using a shell script. Which statement best describes what you should do?

hard

A. Write a shell script with commands to delete temp files, then schedule it with cron

B. Manually type delete commands every day in the terminal

C. Use a graphical tool only, no scripts needed

D. Write a shell script but run it only once manually

Solution

1. Step 1: Understand automation goal

   To automate daily cleaning, you need a script that runs commands automatically.

2. Step 2: Use scheduling tool

   Cron is a tool that runs scripts on a schedule, perfect for daily tasks.

3. Final Answer:

   Write a shell script with commands to delete temp files, then schedule it with cron -> Option A

4. Quick Check:

   Script + cron = daily automation [OK]

Hint: Combine script with cron for daily tasks [OK]

Common Mistakes:

• Thinking manual typing is automation
• Ignoring scheduling tools like cron
• Running script only once instead of daily