Creating a script file (.sh) in Bash Scripting - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

Bash Scripting

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

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

A/bin/bash

B/usr/bin/python

C/bin/sh

D/usr/bin/perl

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong interpreter path like /usr/bin/python.

Forgetting the #! at the start of the line.

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

2fill in blank

medium

Complete the command to make the script file executable.

Bash Scripting

chmod [1] myscript.sh

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

A-r

B+x

C+r

D-w

Attempts:

3 left

💡 Hint

Common Mistakes

Using -r or -w which remove read or write permissions.

Using +r which only adds read permission, not execute.

chmod +x adds execute permission to the script file so it can be run.

3fill in blank

hard

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

Bash Scripting

echo "Current directory is: [1]"

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

A`PWD`

BPWD

C$PWD()

D$PWD

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the $ sign before PWD.

Using PWD as a command instead of a variable.

Use $PWD to get the current directory path as an environment variable.

4fill in blank

hard

Fill both blanks to create a script that prints all arguments passed to it.

Bash Scripting

echo "Arguments: [1]"
for arg in [2]; do
  echo "$arg"
done

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

A"$@"

B$*

C"$*"

D$@

Attempts:

3 left

💡 Hint

Common Mistakes

Using $* which treats all arguments as one string.

Quoting $@ in the loop which breaks iteration.

Use "$@" to print all arguments as separate words and $@ to loop over each argument.

5fill in blank

hard

Fill all three blanks to create a script that checks if a file exists and prints a message.

Bash Scripting

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

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

A-f

Bmyfile.txt

C-d

Dfile.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using -d which checks for directories, not files.

Using the wrong filename or missing quotes if needed.

Use -f to check if a regular file exists, and specify the filename to check.

Practice

1. What is the main purpose of creating a .sh script file in bash?

easy

A. To compile programs

B. To store text documents

C. To save a list of commands to run them later easily

D. To create image files

Solution

1. Step 1: Understand what a script file is

   A .sh file contains bash commands saved to run multiple times without typing again.

2. Step 2: Identify the purpose of saving commands

   Saving commands helps automate tasks and avoid retyping, which matches To save a list of commands to run them later easily.

3. Final Answer:

   To save a list of commands to run them later easily -> Option C

4. Quick Check:

   Script file purpose = save commands [OK]

Hint: Scripts save commands to run anytime without retyping [OK]

Common Mistakes:

• Thinking .sh files are for text or images
• Confusing scripts with compiled programs
• Not knowing scripts automate commands

2. Which line should you add at the very top of a bash script file to specify the interpreter?

easy

A. #!/bin/python

B. #!/bin/bash

C. #!/usr/bin/node

D. #!/bin/shutdown

Solution

1. Step 1: Identify the correct shebang for bash scripts

   The shebang line tells the system which program runs the script. For bash, it is #!/bin/bash.

2. Step 2: Eliminate incorrect interpreters

   Options A, C, and D point to other interpreters or invalid commands.

3. Final Answer:

   #!/bin/bash -> Option B

4. Quick Check:

   Shebang for bash = #!/bin/bash [OK]

Hint: Use #!/bin/bash as first line to run bash scripts [OK]

Common Mistakes:

• Using wrong interpreter path
• Forgetting the #! at the start
• Confusing bash with other languages

3. What will be the output when you run this script named greet.sh?

#!/bin/bash
echo "Hello, $USER!"

medium

A. Syntax error

B. Hello, root!

C. Hello, $USER!

D. Hello, your-username!

Solution

1. Step 1: Understand the variable $USER in bash

   $USER is an environment variable that holds the current user's username.

2. Step 2: Predict the echo output

   The echo command prints "Hello, " followed by the username, so it outputs "Hello, your-username!" where your-username is the actual user.

3. Final Answer:

   Hello, your-username! -> Option D

4. Quick Check:

   $USER expands to username = Hello, your-username! [OK]

Hint: Variables like $USER show your username in scripts [OK]

Common Mistakes:

• Thinking $USER prints literally
• Expecting 'root' always
• Confusing syntax causing errors

4. You wrote a script myscript.sh but when you run ./myscript.sh, it says Permission denied. What is the likely fix?

medium

A. Run chmod +x myscript.sh to make it executable

B. Add #!/bin/bash at the top

C. Rename the file to myscript.txt

D. Run the script with bash myscript.sh only

Solution

1. Step 1: Understand the cause of 'Permission denied'

   This error usually means the file is not executable by the user.

2. Step 2: Make the script executable

   Using chmod +x myscript.sh adds execute permission, allowing ./myscript.sh to run.

3. Final Answer:

   Run chmod +x myscript.sh to make it executable -> Option A

4. Quick Check:

   Permission denied fix = chmod +x [OK]

Hint: Use chmod +x to allow script execution [OK]

Common Mistakes:

• Forgetting to make script executable
• Only adding shebang without permissions
• Renaming file instead of fixing permissions

5. You want to create a script backup.sh that prints "Backup started" and then lists files in the current directory. Which script content is correct?

hard

A. #!/bin/bash
echo "Backup started"
ls

B. echo "Backup started"
ls
#!/bin/bash

C. #!/bin/bash
echo Backup started
ls-l

D. #!/bin/sh
echo "Backup started"
list

Solution

1. Step 1: Check the shebang and commands order

   The script must start with #!/bin/bash to run in bash, then commands follow in order.

2. Step 2: Verify commands and syntax

   #!/bin/bash echo "Backup started" ls has correct shebang, echo with quotes, and ls command to list files. Others have wrong order, missing quotes, or invalid commands.

3. Final Answer:

   #!/bin/bash echo "Backup started" ls -> Option A

4. Quick Check:

   Correct script structure = #!/bin/bash echo "Backup started" ls [OK]

Hint: Start script with #!/bin/bash then commands line by line [OK]

Common Mistakes:

• Placing shebang after commands
• Using wrong commands like 'list'
• Missing quotes around strings