How to List Users in Bash [2 Easy Ways]

To list users in Bash utilize the /etc/passwd file. This file contains a lot of information about the users. You can find a list of normal users, system users, user’s recent activity and many more by searching over the file. To extract information from /etc/passwd file you can use the read or getent command. The getent command has a leverage for this purpose as it is far more useful than listing the users only. The theme of this article is to list users in Bash and determine what kind of users they are by reading and extracting info from the passwd file.

System User and General User

• System users are 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
• A general user is referred to as a regular user. General users do not have administrative privileges like the root user of the 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

You can read the /etc/passwd file or can directly use the getent command to retrieve 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 on users along with their names. The following script is designed to display information about current system users.

To get a list of users by reading the passed file, use the following script:

#!/bin/bash

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

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.

To print the user list using the getent command, go through the below script:

#!/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"

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 of Listing Users in Bash

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

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

Each Field of passwd File

Let’s talk more about the entire passwd file instead of just 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

You 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 the 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 the system and regular user:

grep UID_MIN /etc/login.defs

grep UID_MAX /etc/login.defs

To count the number of system and general users in Bash, please run the following Bash script:

#!/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"

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

Checking the Existence of a User

Using the getent command you can check whether a user with a specific name exists in the system: Here, the user laku exists 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.

People Also Ask

What does users command do in Linux?

The users command only prints the currently logged-in username in Linux. It doesn’t print the whole list of users of the system.

What is the fourth field of the /etc/passwd file?

The fourth field of the /etc/passwd file is for the Group ID, known as GID. The group ID, mainly a number determines the primary group of a user.

How to I list users of a specific group in Linux?

To print all the users of a specific group name, let’s say, group_name, the getent group group_name | cut -d: -f4 command can be used. Just replace the group_name with your desired group name.

How can I switch user in Linux?

To switch between users in Linux, use the su command. In order to switch to a specific user, you simply need to provide the desired username after the su command as a command argument.

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