Linux check user name

UNIX / Linux Command To Check Existing Groups and Users

H ow do I check the existing Linux / UNIX users and groups under Linux operating system?

You can easily check the existing users and groups under a Linux or Unix-like systems such as HP-UX, AIX, FreeBSD, Apple macOS/OS X and more using the following commands:

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	Linux or Unix terminal
Est. reading time	3 minutes

1. getent command : Fetch details for a particular user or group from a number of important text files called databases on a Linux or Unix-like systems. This is portable and recommended way to get information on users and groups.
2. Directly query /etc/passwd for user names or /etc/group file for group names using the grep command/egrep command, and awk command.

Let us see how to check for existing groups and users on Linux and Unix-like systems using command-line.

Method #1: getent command to lookup username and group name

The syntax is as follows to find out if user named foo exists in system:

The syntax is as follows to find out if group named bar exists in system:

Sample demo of all commands:

Fig.01: getent and friends demo on a Linux or Unix system to find out user and group names

Method #2: Find out if user exists in /etc/passwd file

The /etc/passwd file stores essential information required during login. All you have to do is search this file for user name using the following syntax using grep command grep username /etc/passwd
OR we can use the egrep command too:
egrep -i «^ username » /etc/passwd
# search for multiple users
egrep -i «^ username1|username2 » /etc/passwd
For example, find out if vivek user exists or not, enter:
$ egrep -i «^vivek» /etc/passwd
OR
$ egrep -i «^vivek:» /etc/passwd
Sample outputs:

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A quick shell script code:

Normally, exit status is 0 returned if user accounts (lines) are found and 1 otherwise.

Use awk command to search user name

The syntax is as follows to search user named ‘apache’

Find out if group exists in /etc/group file

The /etc/group is an text file which defines the groups to which users belong under Linux and UNIX operating system. Again, you have to search /etc/group file using following syntax:
$ egrep -i «^ groupname » /etc/group
For, example find out if vivek group exists or not, enter:
$ egrep -i «^vivek» /etc/group
# look for vivek or sudo group in /etc/group
$ egrep -i «^(vivek|sudo)» /etc/group

Say hello to id command

The id command is another option to display user / group information for any USERNAME, or the current user. To find out more about user called, tom, enter:
$ id tom
Sample outputs:

id command exit status is 0 returned if user accounts (lines) are found and 1 otherwise. A sample shell script using id command:

How to list all users under Linux or Unix

Try the following syntax:
more /etc/passwd
more /etc/group

Summing up

We explained various Linux and Unix commands that one can use to search for existing users and group in /etc/passwd and /etc/group files, respectively. Make sure you check out the following man pages using the man command:

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Comments on this entry are closed.

don’t forget the “:” after the username otherwise you could end up with this scenario:

$ egrep -i “^vivek” /etc/passwd
vivek:x:1000:1000:Vivek Gite. /home/vivek:/bin/bash
viveks:x:1001:1001:Vivek Smith. /home/viveks:/bin/bash

I really wish the author would update the article to include that because you know 7 years later and still no fix? Worse yet, it’s the first Google search result for “linux check if group exists”.

If you are using NIS do the following:

ypcat passwd | grep vivek

The ‘id’ command should be demonstrated first in this tutorial, as systems using LDAP (other or remote authentication services) will not have users in the local files.

Also why the uses of egrep when a simple grep will do. Keep it simple for the beginners your aiming at.

You should look at getent rather than grepping the local files. “getent passwd” or “getent group” will provide a unified view of users or groups available, respecting your NSS (Name Service Switch) configuration (which is important when you have additional users or groups via LDAP or NIS).

hey Vivek, that was cool..

many of us surely wont care if its grep or egrep ( or fgrep) as long as it does the job and we are taught these wonderful tricks..

Can you please tell me a command to list all of existing user ?

U can try
egrep “*” /etc/passwd
or
egrep “?” /etc/passwd

Very nice site, I could get, what i want in seconds rather than in minutes

`id` comand does not check if groups exist.
`man id`

Print user and group information for the specified USERNAME

the -g flag prints out the primary group id for the user

have you find any solution for that?

Hello
Linux Gurus,
Is there a Command to find out user creation date ?

or any other possible ways to find the same.

please help me
Its urgent.

Thanks In Advance

please tell everyone you ask.
no way to list the user is not disabled in linux.
and has been in how long dis.

The grep approaches are all wrong. You are assuming that an user won’t pick a name that is a started substring of an existing group. Even worse, if you choose to limit the ‘username’ string you could match a group instead of a user. You will mistakenly get output from the script thinking that the user ‘apache’ (or whatever) exists…

You can’t play with strings without semantics. You need a tool that in fact *knows* that what you are talking about is indeed a user.

The best approach for not playing with strings semantics is the id command:

NAME
id – print real and effective user and group IDs

As davidhi mentioned
Using getent is a much better solution in my opinion

# search for user named ‘vivek’
getent passwd vivek

#search for group named ‘vivek’
getent group vivek

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Linux / Unix Shell Script: Get Current User Name

I am working on a shell script. I need to find out the current user name. How do I find out the current user name under Bash or Ksh shell running on Linux or Unix like operating systems? How do I determine the current user account in Linux?

You can use the variables $USER, or $USERNAME which are not Bash builtins. These are, however, set as environmental variables in one of the Bash startup files. You can use the id command to get the same information.

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	Bash/ksh
Est. reading time	1m

a] $USER – Current user name.
b] $USERNAME – Current user name.
c] id command – Print current user name.
d] whoami command – Show current user name.

Syntax

To get the current user name, type:

Get the current user name and store to a shell variable called $u:

The syntax for id command is:

To print numeric UID, run:

The following script reads user name and store to a variable called _user _uid:

Shell script example

Make sure only root user can run the following script:

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A note about $EUID

This variable EUID is readonly. It expands to the effective user ID of the current user, initialized at shell startup. You can use $EUID to find out if user is root or not with the following syntax:

How to determine the current user account in Linux

We can use the who command as follows to print the current user account:
who
whoami
OR use the id command:
id -u -n

Summing up

We explained how you could find and get the current user’s username in a Bash script and shell prompt using various command-line options. See bash man page for more information by typing the following commands:
man bash

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6 Ways to check user information in Linux

Most of us use the id command , and some users filter the user information from the /etc/passwd file.

If you are a beginner for Linux operating systems and want to know more about the /etc/passwd file, please refer the following article.

In general, we use the above two commands to obtain user information. You may ask why to discuss this basic topic. People think there are no alternatives other other than these two commands, but we found that there are other ways to gather user information. Hence, we have created this article to guide you.

In this tutorial, we will discuss all these methods in detail. This is one of the basic commands that help the administrator to find information about a user in Linux.

Remember that everything is stored in a file on Linux, so be careful when handling the configuration file.

We have added several tweaks in this tutorial to collect user information with different aspect.

The following articles may help you to learn more about user management in Linux.

What kind of information is stored in the ‘/etc/passwd’ file

When creating users on Linux the user details are stored in the “/etc/passwd” file.

Each user information in this file is a single line with seven fields and the actual password is stored in the /etc/shadow file.

User information can be queried using these six methods:

• id : Print user and group information for the specified username.
• getent : Get entries from Name Service Switch libraries.
• /etc/passwd file : The /etc/passwd file contain each/every user details as a single line with seven fields.
• finger : User information lookup program
• lslogins : lslogins display information about known users in the system
• compgen : compgen is bash built-in command and it will show all available commands for the user.

1) How to check user information using id command?

The id command stands for identity. It prints real and effective user and group IDs. You can use the id command to print user and group information for the specified user, or for the current user.

Run id command without any username to print the current user information on your terminal.

To collect information on a specific user, use the id command followed by the specific username as shown below:

Details of the above output.

• uid=500(daygeek): It shows the user ID & name
• gid=500(daygeek): It displays the user’s primary group ID & name
• groups=500(daygeek),10(wheel): It displays the user’s secondary groups ID & name

If you want to print multiple user information simultaneously using the id command, use the following small shell script. This script stores the list of users who have a home directory on the system in the variable.

To achieve this, write the following simple bash scripts.

Set an executable permission to “user-info.sh” file.

Finally run the script to get results:

2) Checking user information using getent command

The getent command displays entries from databases supported by the Name Service Switch libraries, which are configured in /etc/nsswitch.conf. The getent command displays user information such as the /etc/passwd file, which displays each user information on a separate line with seven fields.

The seven fields are described below in detail:

• Username (magesh): Username of created user. Characters length should be between 1 to 32.
• Password (x): It indicates that encrypted password is stored at /etc/shadow file.
• User ID (UID-502): It indicates the user ID (UID) each user should be contain unique UID. UID (0-Zero) is reserved for root, UID (1-99) reserved for system users and UID (100-999) reserved for system accounts/groups
• Group ID (GID-503): It indicates the group ID (GID) each group should be contain unique GID is stored at /etc/group file.
• User ID Info (2g Admin — Magesh M): It indicates the command field. This field can be used to describe the user information.
• Home Directory (/home/magesh): It indicates the user home directory.
• shell (/bin/bash): It indicates the user’s bash shell.

If you want to display only the usernames in the getent command output, use the below format:

If you just want to display users that have home directory on system, use the below format:

Use the following format to add a UID to the getent command output:

3) Checking user name and related information in Linux, using /etc/passwd file

The /etc/passwd is a text file containing every user information that is required to log in to the Linux system.

It holds useful information about users such as username, password, user ID, group ID, user ID information, home directory and shell. Each user profile in the “/etc/passwd” file is a single seperate lines with seven fields as described earlier in section #2.

If you only want to display usernames from the /etc/passwd file, use the below format:

If you only want to display users that have home directory on system, use the below format:

Use the following format to add a UID to the following command output:

If you only want to display users that have UID greater than 500 on the system, use the below format:

4) How to check user information using finger Command

The finger command displays information about the system users. It displays the user’s real name, tty name, idle time, login time, home directory and shell name.

Details of the above output.

• Login: User’s login name
• Name: Additional/Other information about the user
• Directory: User home directory information
• Shell: User’s shell information
• LAST-LOGIN: Date of last login and other information

5) Checking user information in Linux, using lslogins command

It displays information about known users in the system. By default it will list information about all the users in the system.

The lslogins utility is inspired by the logins utility, which first appeared in FreeBSD 4.10.

Details of the above output.

• UID: User id
• USER: Name of the user
• PWD-LOCK: password defined, but locked
• PWD-DENY: login by password disabled
• LAST-LOGIN: Date of last login
• GECOS: Other information about the user

6) How to check user & other information in Linux, using compgen command?

The compgen is a bash built-in command and it will show all available commands, aliases, and functions for you as shown below:

Wrapping Up

In this guide, you learned several ways to find user information in Linux.

Please share this to your friends if it is helpful to you.

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