How to List User Groups in Linux/Unix?

You can list all groups a user belongs to in a Linux (or Unix) shell in the following ways:

• Using the id Command;
• Using the groups Command.

Using the id Command

The id command, when used without any flags, displays the user and its group information by default. However, to get only the groups (without additional user information), you can use the command with -Gn flags:

id -Gn [user]

Where the "[user]" is the (optional) username of the user you want to check group information for. When the username is omitted, it defaults to the logged-in user. For example, the following will output the names of the groups the logged-in user is a member of:

id -Gn

Similarly, to only see the groups for a specific user, you can specify the username as an argument to the id command, for example, like so:

id -Gn your_username

Using the groups Command

To list all groups a user is a member of, you can use the groups command. It has the following syntax:

groups [user]

Where "[user]" can be the username of the user you wish to output the groups for. For example:

groups your_username

If you omit the username, then it will display the groups for the logged-in user.

The man groups command suggests that the groups utility has been obsoleted by the id(1) utility, and is equivalent to the "id -Gn [user]" command.