What a shell script is in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a shell script with the correct shebang line.

Bash Scripting

#![1]
echo "Hello, world!"

Drag options to blanks, or click blank then click option'

A/usr/bin/python

B/usr/bin/node

C/bin/shutdown

D/bin/bash

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong interpreter path like /usr/bin/python for a shell script.

Forgetting the #! at the start of the script.

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

2fill in blank

medium

Complete the code to assign a value to a variable in a shell script.

Bash Scripting

name=[1]
echo "Hello, $name!"

Drag options to blanks, or click blank then click option'

A"Alice"

BAlice

C'Alice'

D$Alice

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning a value without quotes can cause errors if the value has spaces.

Using single quotes prevents variable expansion but is okay for plain strings.

In shell scripts, variable values with spaces or special characters should be quoted using double quotes.

3fill in blank

hard

Fix the error in the script to correctly print the current directory.

Bash Scripting

echo "Current directory is: [1]"

Drag options to blanks, or click blank then click option'

Apwd

B$pwd

C$(pwd)

D`pwd`

Attempts:

3 left

💡 Hint

Common Mistakes

Writing pwd without command substitution just prints the word 'pwd'.

Using $pwd tries to expand a variable named pwd which is usually empty.

Using $(pwd) runs the pwd command and inserts its output into the echo statement.

4fill in blank

hard

Fill both blanks to create a loop that prints numbers 1 to 5.

Bash Scripting

for i in [1]
do
  echo [2]
done

Drag options to blanks, or click blank then click option'

A1 2 3 4 5

B$i

D1..5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1..5 does not create a list in bash.

Printing i without $ prints the letter 'i' instead of the variable value.

The loop iterates over the list '1 2 3 4 5' and prints each value stored in $i.

5fill in blank

hard

Fill all three blanks to create a conditional that checks if a file exists.

Bash Scripting

if [[ -[1] [2] ]]; then
  echo "File [3] exists."
else
  echo "File does not exist."
fi

Drag options to blanks, or click blank then click option'

Ae

Bmyfile.txt

Cf

Dfile.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using -f checks if it is a regular file but -e is more general.

Using different filenames in the test and echo causes confusion.

The -e flag checks if a file exists. The filename is 'myfile.txt' used in both places.

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