First Bash script in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the first line in a Bash script that tells the system which interpreter to use?

The first line is called the shebang. It looks like #!/bin/bash and tells the system to use the Bash shell to run the script.

beginner

How do you make a Bash script executable?

Use the command chmod +x scriptname.sh to give execute permission to your script.

beginner

What command runs a Bash script named hello.sh in the current directory?

Run the script with ./hello.sh if it has execute permission.

beginner

What does this simple Bash script do?

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

It prints the text Hello, world! to the screen.

beginner

Why is it important to save your Bash script with a .sh extension?

The .sh extension helps you and others recognize the file as a shell script, but it is not required for execution.

What does the shebang line #!/bin/bash do in a Bash script?

A Comments out the line

B Specifies the script interpreter

C Runs the script automatically

D Defines a variable

The shebang line tells the system which program to use to run the script.

Which command makes a Bash script executable?

A chmod +x script.sh

B run script.sh

C bash script.sh

D edit script.sh

The chmod +x command adds execute permission to the script.

How do you run a Bash script named myscript.sh in the current folder?

A myscript.sh

B execute myscript.sh

C bash run myscript.sh

D ./myscript.sh

Use ./myscript.sh to run the script if it has execute permission.

What does the command echo "Hello" do in a Bash script?

A Deletes Hello

B Creates a file named Hello

C Prints Hello to the screen

D Runs a program called Hello

The echo command prints text to the screen.

Is the .sh extension required to run a Bash script?

A No, but it helps identify the file

B Yes, it is required

C Only on Windows

D Only if the script is large

The extension is not required but is a helpful convention.

Describe the steps to create and run your first Bash script.

Think about writing, saving, permission, and running.

Explain the purpose of the shebang line in a Bash script and what happens if it is missing.

Focus on interpreter selection and script execution.

Practice

1. What is the purpose of the first line #!/bin/bash in a Bash script?

easy

A. It comments out the first line so it is ignored.

B. It prints a welcome message when the script runs.

C. It sets the script to run in the background automatically.

D. It tells the system to use the Bash shell to run the script.

Solution

1. Step 1: Understand the shebang line

   The line #!/bin/bash is called a shebang and tells the system which interpreter to use.

2. Step 2: Identify its role in script execution

   This line ensures the script runs with the Bash shell, not another shell or program.

3. Final Answer:

   It tells the system to use the Bash shell to run the script. -> Option D

4. Quick Check:

   Shebang = Bash interpreter [OK]

Hint: Shebang line always points to the shell interpreter [OK]

Common Mistakes:

• Thinking it prints a message
• Confusing it with a comment
• Assuming it runs script in background

2. Which of the following is the correct way to print "Hello, World!" in a Bash script?

easy

A. echo "Hello, World!"

B. printf(Hello, World!)

C. console.log("Hello, World!")

D. print("Hello, World!")

Solution

1. Step 1: Identify the Bash command for output

   In Bash, echo is used to print text to the screen.

2. Step 2: Check syntax correctness

   echo "Hello, World!" correctly prints the message with quotes around the string.

3. Final Answer:

   echo "Hello, World!" -> Option A

4. Quick Check:

   Print command in Bash = echo [OK]

Hint: Use echo to print text in Bash scripts [OK]

Common Mistakes:

• Using print() like in Python
• Using console.log() from JavaScript
• Missing quotes in printf

3. What will be the output of this Bash script?

#!/bin/bash
echo "Start"
echo "End"

medium

A. Start\nEnd

B. Start
End (two lines)

C. Start
End

D. Start End

Solution

1. Step 1: Understand echo behavior

   The echo command prints text followed by a new line by default.

2. Step 2: Analyze the script output

   Two echo commands print "Start" and "End" each on its own line.

3. Final Answer:

   Start End (two lines) -> Option B

4. Quick Check:

   echo adds newline = two lines output [OK]

Hint: Each echo prints on a new line by default [OK]

Common Mistakes:

• Thinking echo prints on same line
• Confusing \n as literal text
• Ignoring new line after echo

4. Identify the error in this Bash script:

#!/bin/bash
echo Hello World

medium

A. Missing quotes around Hello World

B. echo command is misspelled

C. No error, script runs fine

D. Missing shebang line

Solution

1. Step 1: Check script syntax

   The script has a correct shebang line and uses echo properly.

2. Step 2: Understand echo argument rules

   Quotes are optional if no special characters or spaces that confuse shell; here it works fine.

3. Final Answer:

   No error, script runs fine -> Option C

4. Quick Check:

   echo without quotes works here [OK]

Hint: Quotes optional if no special chars or spaces [OK]

Common Mistakes:

• Assuming quotes are always required
• Thinking shebang is missing
• Believing echo is misspelled

5. You want to write a Bash script that prints your name and then the current date. Which script below will do this correctly?

hard

A. #!/bin/bash
echo "My name is Alice"
date

B. #!/bin/bash
print "My name is Alice"
date

C. #!/bin/bash
echo My name is Alice
current_date

D. #!/bin/bash
echo "My name is Alice"; date %Y-%m-%d

Solution

1. Step 1: Check commands for printing text and date

   echo prints text; date prints current date and time.

2. Step 2: Verify script correctness

   #!/bin/bash echo "My name is Alice" date uses echo correctly and calls date without errors.

3. Final Answer:

   #!/bin/bash\necho "My name is Alice"\ndate -> Option A

4. Quick Check:

   Use echo and date commands correctly [OK]

Hint: Use echo for text and date command for current date [OK]

Common Mistakes:

• Using print instead of echo
• Calling undefined commands like current_date
• Incorrect date command syntax