How to List Users in Bash [2 Easy Ways]

The etc/passwd file contains a lot of information about users in Unix-like operating system. One can find a list of normal users, system users, user’s recent activity and many more by searching over the etc/passwd file. In this article, I’ll demonstrate how to list users in Bash and determine what kind of users they are. In the process of doing so, I will use read, cut and many other basic Bash commands that you might already know.

Key Takeaways

• Finding a list of users.
• Identifying system users and normal users.
• User’s most recent action on the system.

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System User and General User

• System User

System users are also known as privileged users. These are accounts on the system with elevated privileges. These users have more extensive control over the system and can perform tasks that regular users cannot. They have access to critical system files, configuration settings, and administrative tools. In Unix-based systems like Linux, the root user is the superuser with complete control over the system

• General User

A general user also referred to as a regular user. General users do not have administrative privileges like the root user of Unix system. General users can perform activities, such as running applications, accessing personal files and using the system’s basic features.

2 Ways of Getting a List of Users in Bash

One can read the /etc/passwd file or can directly use the getent command to retrieve the information about users. Read the methods below to know more about these.

Method 01: How to Get a List of Users by Reading the passwd File

The passwd file is located in the etc folder of the system. This file contains information of users along with their names. The following script is designed to display information about current system users.

Steps to Follow >

❶ At first, launch an Ubuntu Terminal.

❷ Write the following command to open a file named user.sh in the build-in nano editor:

nano user.sh

❸ Copy the following scripts and paste them into nano. Press CTRL+O and ENTER to save the file; CTRL+X to exit. Alternatively, copy the following script. Paste the script in a text editor and save it as .sh file.

Script (user.sh) >

#!/bin/bash

while IFS=: read -r username _ _ _ _ _ _
do
echo "$username"
done < /etc/passwd

❹ Use the following two commands to make both file executable:

chmod u+x user.sh

❺ Run the user.sh script by the following command:

./user.sh

Once executed the script will print a whole list of users of the system. If you go down you can also see the currently logged-in username.As you can see the currently logged-in username of my system is printed at the end of the list.

Method 02: Printing User List Using the getent Command

The getent command is another built-in command to get the list of users in the system. Here I am providing a Bash script to print all the users of the system.

Script (getent.sh) >

#!/bin/bash

# Retrieve the list of users using getent command and store it in a variable
user_list=$(getent passwd | cut -d: -f1)
# Print the list of users
echo "List of users:"
echo "$user_list"

Run the getent.sh script by the following command:

./getent.sh

Once executed the script will print all the users including system users and general users as you can the above image.

Comparative Analysis of Methods

Here is a comparative analysis between the above-discussed methods. Take a look at the analysis to determine which method suits your need.

I think the best approach here is to use the getent command as it can extract more information about user other than the username only. Moreover the getent is straightforward and don’t need to extract any field.

Each Field of passwd File

Let’s talk more about the passwd file instead of the first field of each line only. Each line of the passwd file has seven different fields separated by a colon. For example, consider one of the outputs of the getent passwd command.

Counting System and General User

One can easily identify general users and system users with basic knowledge of Bash scripting. In the script below, I am going to count different types of users currently in the system based on UID range.

UIDs below 1000 are typically reserved for system users, while those 1000 and above are for regular user accounts. Run the following two commands to find the UID range for system and regular user.

grep UID_MIN /etc/login.defs

grep UID_MAX /etc/login.defs

Script (count.sh) >

#!/bin/bash

# Number of total user
total_user=$(wc -l < /etc/passwd)
echo "Number of total users in the system: $total_user"

# Loop through all users and check if they have superuser privileges
regular_user=0

while IFS=: read -r username _ uid _ _ _ _; do
if (( uid >= 1000 )); then
regular_user=$((regular_user + 1))
fi
done < /etc/passwd

system_user=$((total_user - regular_user))
echo "Number of regular users in the system: $regular_user"
echo "Number of system users in the system: $system_user"

Run the count.sh script by the following command:

./count.sh

Here the script shows the number of total users in the system is 48. Among them, 2 users are regular user rest of them are system users.

Checking the Existence of a User

Using the getent command one can check whether a user with a specific name exists in the system.Here the user laku exist in the system hence getent passwd laku shows the output. However, getent passwd alina doesn’t give any output because user alina doesn’t exist in the system.

You can also list down all the group users using the following command.

getent group | cut -d: -f1

Conclusion

In conclusion, Getting a list of users in Bash is an important aspect of system administration and security. Knowing all present users of a system allows administrators to have better control over access and permissions. Hope now you can easily get all the users and groups with a simple Bash script.

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