Get current user name linux

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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whoami Command: Find the Current User in Linux

Find information about your current Linux user account

What to Know

• Type whoami to display the current username. If whoami isn’t installed, type id -un.
• More id commands: Show user ID without username = id -u. Show effective group -g. Show group name = id -gn.
• Show every group ID the user belongs to = id -G. Show every group name the user belongs = id -Gn.

This article explains how to use the whoami and id commands to find the user account you’re logged into, group IDs, and group names. Also included are instructions for using the —help switch and how to view the current version of whoami or id.

Use whoami to Display Your Username

To use the terminal window to display the user you’re actively logged in as, type the following command:

To quickly see how this works with another user account (if you haven’t made any other users in Linux), use the sudo command to log in as root:

Then, if you run the whoami command again, you’ll be told that you’re root.

How to Do It With id -un

In a strange circumstance where whoami isn’t installed, there is another command you can use to display your current username.

The result is exactly the same as the whoami command, so in this example, it would display jacob.

The id command can show more than the current user. It can also show the user id, group id, and groups to which the user belongs. For example, to show only the effective group the user belongs to, type the following:

The above command only shows the group id. It doesn’t show the group name. To show the effective group name, execute this command:

You can display every group id that a user belongs to by entering this:

The above command only shows the group ids. You can also use the Linux id command to display the group names:

If you want to display your user id without the username, run the following command:

More Information

You can use the —help switch with either whoami or id to find the current man page for each program.

To see the current version of id or whoami, use the following commands:

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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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How to get the username in C/C++ in Linux?

How can I get the actual «username» without using the environment ( getenv , . ) in a program? Environment is C/C++ with Linux.

6 Answers 6

The function getlogin_r() defined in unistd.h returns the username. See man getlogin_r for more information.

Its signature is:

Needless to say, this function can just as easily be called in C or C++.

Just take main lines and encapsulate it in class:

Another way is this —

Use char *cuserid(char *s) found in stdio.h .

See for more details:

working a little bit through modern c++ specs

Today I had to do the same thing, but didn’t like to include any OS specific headers. So here is what you can do in a cross-platform way without resorting to any Linux/Windows specific headers:

This works just fine on both Linux and Windows and is C++11 compatible!

Not the answer you’re looking for? Browse other questions tagged c++ c linux posix or ask your own question.

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