[Linux] Bash id usage: Display user and group information

Overview

The id command in Bash is used to display the user and group information for the current user or a specified user. It provides details such as the user ID (UID), group ID (GID), and the groups to which the user belongs.

Usage

The basic syntax of the id command is as follows:

id [options] [username]

Common Options

• -u: Display only the effective user ID.
• -g: Display only the effective group ID.
• -G: Display all group IDs the user belongs to.
• -n: Display names instead of numeric IDs.
• -r: Display the real ID instead of the effective ID.

Common Examples

Here are some practical examples of using the id command:

1. Display information for the current user:

   id
   

2. Display information for a specific user (e.g., username):

   id username
   

3. Display only the effective user ID:

   id -u
   

4. Display only the effective group ID:

   id -g
   

5. Display all group IDs for the current user:

   id -G
   

6. Display user information with names instead of numeric IDs:

   id -n
   

Tips

• Use id without any options to quickly check your own user and group information.
• Combine options for more specific queries, such as id -Gn to get the group names of the current user.
• If you encounter permission issues, ensure you have the necessary rights to view information for other users.