User account management script in Bash Scripting - Step-by-Step Execution

Concept Flow - User account management script

Start Script

↓

Check Input Arguments

↓

Match Command: add|delete|list

↓

Add User

↓

Show Result

↓

End Script

The script starts, checks the command given, runs the matching user action (add, delete, or list), then shows the result and ends.

Execution Sample

Bash Scripting

#!/bin/bash
if [ "$1" = "add" ]; then
  sudo useradd "$2"
  echo "User $2 added"
elif [ "$1" = "delete" ]; then
  sudo userdel "$2"
  echo "User $2 deleted"
else
  cut -d: -f1 /etc/passwd
fi

This script adds or deletes a user based on the first argument, or lists users if no valid command is given.

Execution Table

Step	Input Arguments	Condition Checked	Action Taken	Output
1	add alice	$1 == 'add'?	Yes, run useradd alice	User alice added
2	delete bob	$1 == 'add'?	No, check $1 == 'delete'?	No
3	delete bob	$1 == 'delete'?	Yes, run userdel bob	User bob deleted
4	list	$1 == 'add'?	No	No
5	list	$1 == 'delete'?	No	No
6	list	Else branch	Run cut to list users	(list of users)
7	unknown	$1 == 'add'?	No	No
8	unknown	$1 == 'delete'?	No	No
9	unknown	Else branch	Run cut to list users	(list of users)

💡 Script ends after performing the matched action or listing users.

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 6	After Step 9
$1 (command)	none	add	delete	list	unknown
$2 (username)	none	alice	bob	none	none

Key Moments - 3 Insights

Why does the script list users when the command is unknown?

Because the else branch runs when $1 is not 'add' or 'delete', as shown in execution_table rows 6 and 9.

What happens if no username is given with 'add' or 'delete'?

The script tries to run useradd or userdel with an empty username, which will cause an error. This is not handled in the current script.

Why do we use sudo before useradd and userdel?

Because adding or deleting users requires admin rights. Without sudo, these commands will fail unless run as root.

Visual Quiz - 3 Questions

Look at the execution table, what is the output when the input is 'add alice'?

A (list of users)

B User alice deleted

C User alice added

D No output

💡 Hint

Check row 1 in the execution_table for input 'add alice'.

At which step does the script run the command to delete a user?

A Step 3

B Step 6

C Step 1

D Step 9

💡 Hint

Look for the action 'run userdel bob' in the execution_table.

If the input is 'unknown', what branch does the script take?

A Add user branch

B Else branch to list users

C Delete user branch

D Script exits without output

💡 Hint

See rows 7-9 in the execution_table for input 'unknown'.

Concept Snapshot

User account management script syntax:
if [ "$1" = "add" ]; then
  sudo useradd "$2"
elif [ "$1" = "delete" ]; then
  sudo userdel "$2"
else
  cut -d: -f1 /etc/passwd
fi

Use first argument as command, second as username.
Add/delete users or list all users if unknown command.

Full Transcript

This script starts by checking the first input argument. If it is 'add', it runs the command to add a user with the second argument as username and prints confirmation. If it is 'delete', it deletes the user named by the second argument and prints confirmation. If the command is anything else, it lists all users on the system by reading /etc/passwd. Variables $1 and $2 hold the command and username respectively. The script ends after performing the requested action. Using sudo is necessary for useradd and userdel commands. If no username is given for add or delete, the script will try to run the command with an empty username, which causes an error. This script is a simple example of user account management in bash.