Linux which groups exist

Linux/UNIX: Find Which Groups Do I Belong To

H ow do I find out in which groups do I belong to on Linux or Unix-like operating systems? How can I find out my group membership so that I can determine access to devices and files on Linux/Unix operating systems?

A user can be in any number of groups apart from his/her default group. Groups are created and managed by root user. You cannot edit or modify your own ownership. However Linux allows you to view in which groups you are by using the groups command. This is useful to find out if you can access:

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	None
Est. reading time	1m

1. Directories
2. Files
3. Devices
4. Burn CD/DVD
5. Backup files
6. Restart system services
7. Play music and video and more.

Task: Display or print the groups a user is in

Type the whoami command to display your user ID:
$ whoami
Sample outputs:

See which groups your Linux/Unix user belongs to

Type the groups command to show which groups your Unix or Linux user belongs to:
$ groups
Sample outputs:

So my default group is vivek and I am a member of dialout, cdrom, floppy, audio, video plugdev group. You can also use id command to print both numeric and name based group id:
$ id
Output:

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The id command is preferred command to list groups a user belongs to On Linux or Unix-like operating systems:
$ groups
$ groups userNameHere
$ id -Gn
$ id -Gn userNameHere
Sample outputs:

Animated gif 01: groups and id command to display groups a user belongs to

See also

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Linux Show The Groups a User Is In

Example

pen a command-line terminal (select Applications > Accessories > Terminal), and then type:
$ groups
Sample outputs:

You are part of all of the above groups. To find group memebership for root user, enter:
$ groups root
Sample outputs:

Please note that (from the groups man page):

Primary and supplementary groups for a process are normally inherited from its parent and are usually unchanged since login. This means that if you change the group database after logging in, groups will not reflect your changes within your existing login session. Running `groups’ with a list of users causes the user and group database to be consulted afresh, and so will give a different result.

You can also use the id command as follows to get the same information:
$ id -Gn
$ id -Gn userName
$ id -Gn vivek

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How Do I Find Out My Primary Group Membership?

Type the following command:
$ getent group userName
$ getent group vivek
Sample outputs:

In this example, user vivek has group id # 1000 and has group name vivek for primary group membership.

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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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Category	List of Unix and Linux commands
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Processes Management	bg • chroot • cron • disown • fg • glances • gtop • jobs • killall • kill • pidof • pstree • pwdx • time • vtop
Searching	ag • grep • whereis • which
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WireGuard VPN	Alpine • CentOS 8 • Debian 10 • Firewall • Ubuntu 20.04

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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