User account management script in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this user creation script snippet?

Consider this bash script snippet that attempts to add a user and set a password. What will be the output if the user 'alice' already exists on the system?

Bash Scripting

if id "alice" &>/dev/null; then
  echo "User alice already exists"
else
  sudo useradd alice
  echo "alice:password123" | sudo chpasswd
  echo "User alice created"
fi

A User alice created

B Error: useradd command not found

C User alice already exists

D Password set for alice

💡 Hint

The script checks if the user exists before creating.

The script uses 'id alice' to check if the user exists. If yes, it prints 'User alice already exists' and skips creation.

📝 Syntax

intermediate

Identify the syntax error in this user deletion script

Which option correctly fixes the syntax error in this bash script that deletes a user and their home directory? Original snippet: sudo userdel -r $username if [ $? -eq 0 ] echo "User deleted" else echo "Failed to delete user" fi

Bash Scripting

sudo userdel -r $username
if [ $? -eq 0 ]; then
  echo "User deleted"
else
  echo "Failed to delete user"
fi

A Add 'then' after the if condition: if [ $? -eq 0 ]; then

B Replace 'fi' with 'end'

C Remove the else block entirely

D Add a semicolon after echo statements

💡 Hint

Bash if statements require 'then' after the condition.

The 'if' statement must have 'then' after the condition to be valid syntax.

🔧 Debug

advanced

Why does this script fail to add multiple users from a file?

This script reads usernames from a file and tries to add them. Why does it fail to add any users? Script: while read user; do sudo useradd $user echo "Added $user" done < users.txt

Bash Scripting

while read user; do
  sudo useradd "$user"
  echo "Added $user"
done < users.txt

A The script lacks quotes around $user causing word splitting

B The script does not handle empty lines or spaces in usernames

C The input redirection syntax is incorrect

D The read command trims trailing spaces causing empty usernames

💡 Hint

Variables with spaces need quotes in bash commands.

Without quotes, usernames with spaces split into multiple arguments causing useradd to fail.

🚀 Application

advanced

What is the value of the variable 'count' after running this script?

This script counts how many users in the system have a home directory under /home. What is the value of 'count' after execution? Script: count=0 for user in $(cut -d: -f1 /etc/passwd); do home_dir=$(getent passwd "$user" | cut -d: -f6) if [[ $home_dir == /home/* ]]; then ((count++)) fi done echo $count

Bash Scripting

count=0
for user in $(cut -d: -f1 /etc/passwd); do
  home_dir=$(getent passwd "$user" | cut -d: -f6)
  if [[ $home_dir == /home/* ]]; then
    ((count++))
  fi
done
echo $count

A The total number of users in /etc/passwd

B Zero, because the script has a syntax error

C The number of users without home directories

D The number of users with home directories under /home

💡 Hint

The script filters users by home directory path prefix.

The script increments count only for users whose home directory starts with /home.

🧠 Conceptual

expert

Which option best describes the purpose of the 'usermod' command in user management scripts?

In bash scripts managing users, what is the primary purpose of the 'usermod' command?

A To create a new user account with default settings

B To modify existing user account properties like username, home directory, or shell

C To delete a user account and remove its files

D To list all current user accounts on the system

💡 Hint

Think about changing user details without deleting or creating.

The 'usermod' command changes properties of existing users, such as username or shell.

Practice

1. What is the main purpose of a bash script that manages user accounts with commands like useradd and userdel?

easy

A. To change the system hostname

B. To automate adding, deleting, and listing users on the system

C. To update software packages automatically

D. To monitor network traffic

Solution

1. Step 1: Understand the commands used

   The commands useradd and userdel are specifically for managing user accounts on Linux systems.

2. Step 2: Identify the script's goal

   Since the script uses these commands, its main purpose is to automate user account management tasks like adding, deleting, and listing users.

3. Final Answer:

   To automate adding, deleting, and listing users on the system -> Option B

4. Quick Check:

   User management commands = automate user tasks [OK]

Hint: Look for user management commands like useradd/userdel [OK]

Common Mistakes:

• Confusing user management with system updates
• Thinking it changes network settings
• Assuming it modifies system hostname

2. Which of the following is the correct syntax to add a new user named alice in a bash script?

easy

A. createuser alice

B. adduser alice

C. newuser alice

D. useradd alice

Solution

1. Step 1: Recall the standard command for adding users

   The standard Linux command to add a user is useradd.

2. Step 2: Match the command with the username

   Using useradd alice correctly adds a user named alice.

3. Final Answer:

   useradd alice -> Option D

4. Quick Check:

   Standard add user command = useradd [OK]

Hint: Remember: useradd is the standard command to add users [OK]

Common Mistakes:

• Using adduser which may not be available on all systems
• Typing createuser or newuser which are invalid commands
• Confusing commands with other system utilities

3. What will be the output of this bash snippet if the script is run with root privileges?

if id "bob" &>/dev/null; then
  echo "User exists"
else
  echo "User does not exist"
fi

medium

A. User does not exist

B. User exists

C. Syntax error

D. Permission denied

Solution

1. Step 1: Understand the id command usage

   The command id "bob" checks if user bob exists. If bob does not exist, it returns an error.

2. Step 2: Analyze the if condition and output

   The script redirects errors to /dev/null, so if bob does not exist, the else branch runs, printing "User does not exist".

3. Final Answer:

   User does not exist -> Option A

4. Quick Check:

   id command fails = else branch runs [OK]

Hint: id command success means user exists; else means no user [OK]

Common Mistakes:

• Assuming output shows error messages
• Thinking permission issues cause output
• Confusing command syntax with errors

4. Identify the error in this script snippet that tries to delete a user named charlie:

userdel charlie
if [ $? -eq 0 ]; then
  echo "User deleted"
else
  echo "Failed to delete user"
fi

medium

A. Missing sudo or root privileges to run userdel

B. Incorrect syntax for if statement

C. userdel command should be userremove

D. No error, script works fine

Solution

1. Step 1: Check command permissions

   The userdel command requires root privileges. Running it without sudo or as root will fail.

2. Step 2: Verify script syntax and commands

   The if statement syntax and command are correct, but permission issues cause failure.

3. Final Answer:

   Missing sudo or root privileges to run userdel -> Option A

4. Quick Check:

   userdel needs root = permission error if missing [OK]

Hint: Remember: userdel needs root or sudo to succeed [OK]

Common Mistakes:

• Thinking userdel syntax is wrong
• Using wrong command name like userremove
• Ignoring permission requirements

5. You want to write a bash script that adds multiple users from a list in a file users.txt. Which script snippet correctly reads each username and adds the user, skipping empty lines?

hard

A. read users.txt | while read user; do
useradd $user
done

B. for user in $(cat users.txt); do
useradd $user
done

C. while read user; do
[ -z "$user" ] && continue
useradd "$user"
done < users.txt

D. cat users.txt | while useradd; do
echo $user
done

Solution

1. Step 1: Understand reading lines safely

   Using while read user reads each line safely, including spaces, and allows skipping empty lines.

2. Step 2: Check skipping empty lines and adding users

   The condition [ -z "$user" ] && continue skips empty lines. Then useradd "$user" adds the user correctly.

3. Final Answer:

   while read user; do [ -z "$user" ] && continue useradd "$user" done < users.txt -> Option C

4. Quick Check:

   Safe line read + skip empty + add user = while read user; do [ -z "$user" ] && continue useradd "$user" done < users.txt [OK]

Hint: Use while read and check empty lines to avoid errors [OK]

Common Mistakes:

• Using for loop with word splitting causing errors
• Incorrect pipe usage with cat and while
• Not skipping empty lines causing useradd errors