Linux get user shell

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.

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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How do I find out what shell I am using on Linux/Unix?

B oth Linux and Unix provides various shell out of the box. One can find bash (Bourne Again shell), ksh (Korn shell), csh (C shell)/tcsh (TC shell), sh (Bourne shell) and more installed by default. However, how do you check which shell am I using? What is the best way to find out what shell I am using on Linux? The echo $SHELL is not so reliable. This page explains how to find out which shell I am using at a Linux, MacOS, FreeBSD, or Unix-like systems.

How can I find out what shell I am using?

The following echo command or printf command should work:
echo «$SHELL»
OR
printf «My current shell — %s\n» «$SHELL»
Please note that $SHELL is the shell for the current user but not necessarily the shell that is running at the moment. Try the following examples

How do I check which shell am I using?

Here is another old good Unix trick. Use the ps command with -p option. The following command selects the processes whose process ID numbers appear in pid. Use the following command to find out which shell you are in:
ps -p $$
Sample outputs:

So what is a $ argument passed to the -p option? Remember $ returns the PID (process identification number) of the current process, and the current process is your shell. So running a ps on that number displays a process status listing of your shell. In that listing, you will find the name of your shell (look for CMD column).
ps -p $$
Sample outputs:

From my Linux box:
ps -p $$
Sample outputs:

You can store your shell name in a variable as follows :
MYSHELL=`ps -hp $$|awk ‘‘`
Please note those are backquotes, not apostrophes. Or better try out the following if you have a bash shell:
MYSHELL=$(ps -hp $$|awk ‘‘)
Another option is as follows:
echo $0
OR
printf «%s\n» $0
Sample outputs from the above commands:

Fig.01: Linux check which shell am I using

How do I check how many shells are installed on my Linux box?

The /etc/shells is a text file which contains the full pathnames of valid login shells. Type the following [nixmd name=”cat”] to see list how many shells are installed on your Linux or Unix box:
cat /etc/shells

Use /etc/shells file to check how many shells are installed on your system

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Okay, so when I open the Terminal app, which shell is opened by default?

Your default shell is defined in /etc/passwd file. So try the following grep command:

How to check which shell am I using:

Use the following Linux or Unix commands:

1. ps -p $$ – Display your current shell name reliably.
2. echo «$SHELL» – Print the shell for the current user but not necessarily the shell that is running at the movement.
3. echo $0 – Another reliable and simple method to get the current shell interpreter name on Linux or Unix-like systems.
4. readlink /proc/$$/exe – Another option to get the current shell name reliably on Linux operating systems.
5. cat /etc/shells – List pathnames of valid login shells currently installed
6. grep «^$USER» /etc/passwd – Print the default shell name. The default shell runs when you open a terminal window.
7. chsh -s /bin/ksh – Change the shell used from /bin/bash (default) to /bin/ksh for your account

Conclusion

Sometimes things are not easy as they seem, and this page is the perfect example of it. I hope you found the suggestion useful when it comes to checking your current running shell. Bash users can display shell version by typing the following command:
$ bash —version
Here is what I got from my Ubuntu Linux 20.04 LTS desktop:

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Linux List All Users In The System Command

Table of contents

Linux list all users account using the /etc/passwd file

In order to list all users on Linux, use the cat command as follows:
$ cat /etc/passwd
Here is what I see:

Each line in the file has seven fields as follows. For example, consider the following line:
vnstat:x:131:137:vnstat daemon. /var/lib/vnstat:/usr/sbin/nologin
Where,

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• vnstat – The user name or login name.
• x – Encrypted password is stored in the /etc/shadow file.
• 131 – UID (user ID number)
• 137 – Primary GID (group ID number)
• vnstat daemon – GECOS. It may includes user’s full name (or application name, if the account is for a program), building and room number or contact person, office telephone number, home telephone number and any other contact information.
• /var/lib/vnstat – Home directory for the user.
• /usr/sbin/nologin – Login shell for the user. Pathnames of valid login shells comes from the /etc/shells file.

How to list users in Linux using pagers

Of course we can use pagers such as more/less commands as follows to view the /etc/passwd file:
$ more /etc/passwd
$ less /etc/passwd
Sample outputs:

Fig.01: List users using /etc/passwd

Linux list user names only

To list only usernames type the following awk command:
$ awk -F’:’ ‘< print $1>‘ /etc/passwd
Sample outputs:

Another option is to use the cut command:
$ cut -d: -f1 /etc/passwd

Get a list of all users using the getent command

To get a list of all Linux users you can type the following getent command:
$ getent passwd
$ getent passwd | grep tom
## get a list all users ##
$ getent passwd | cut -d: -f1
## count all user accounts using the wc ##
$ getent passwd | wc -l
One can use the compgen command on Linux to list users and other resources too:
$ compgen -u

Find out whether a user account exists in the Linux server

We can use above commands to see whether a user exists in the Linux machine as follows using the grep command:

A simplified command would be:

How to count user accounts in the Linux server

Want to get user accounts count on your system? Try the wc command as follows:
$ compgen -u | wc -l
$ getent passwd | wc -l

A Note About System and General Users

Each user has numerical user ID called UID. It is defined in /etc/passwd file. The UID for each user is automatically selected using /etc/login.defs file when you use useradd command. To see current value, enter:
$ grep «^UID_MIN» /etc/login.defs
$ grep UID_MIN /etc/login.defs
Sample outputs:

1000 is minimum values for automatic uid selection in useradd command. In other words all normal system users must have UID >= 1000 and only those users are allowed to login into system if shell is bash/csh/tcsh/ksh etc as defined /etc/shells file. Type the following command to list all login users:

To see maximum values for automatic uid selection in the useradd command, enter:
$ grep «^UID_MAX» /etc/login.defs
Sample outputs:

In other words, all normal system users must have UID >= 1000 (MIN) and UID /etc/shells file. Here is an updated code to get details:

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3 Ways to Change a Users Default Shell in Linux

In this article, we will describe how to change a user’s shell in Linux. The shell is a program that accepts and interprets commands; there are several shells such as bash, sh, ksh, zsh, fish and many other lesser known shells available on Linux.

Bash (/bin/bash) is a popular shell on most if not all Linux systems, and it’s normally the default shell for user accounts.

There are several reasons for changing a user’s shell in Linux including the following:

1. To block or disable normal user logins in Linux using a nologin shell.
2. Use a shell wrapper script or program to login user commands before they are sent to a shell for execution. Here, you specify the shell wrapper as a user’s login shell.
3. To meet a user’s demands (wants to use a specific shell), especially those with administrative rights.

When creating user accounts with the useradd or adduser utilities, the —shell flag can be used to specify the name of a user’s login shell other than that specified in the respective configuration files.

A login shell can be accessed from a text based interface or via a SSH from remote Linux machine. However, if you login via a graphical user interface (GUI), you can access the shell from a terminal emulators like xterm, konsole and many more.

Let’s first list all available shells on your Linux system, type.

Before you proceed any further, note that:

• A user can change their own shell to any thing: which, however must be listed in the /etc/shells file.
• Only root can run a shell not listed in /etc/shells file.
• If an account has a restricted login shell, then only root can change that user’s shell.

Now let’s discuss three different ways to change Linux user shell.

1. usermod Utility

usermod is a utility for modifying a user’s account details, stored in the /etc/passwd file and the -s or —shell option is used to change the user’s login shell.

In this example, we’ll first check user tecmint’s account information to view his default login shell and then change its login shell from /bin/sh to /bin/bash as follows.

Change User Shell using Usermod

2. chsh Utility

chsh is a command line utility for changing a login shell with the -s or –shell option like this.

Change User Shell Using chsh

The two methods above all modify the shell specified in /etc/passwd file which you can edit manually as in the third method below.

3. Change User Shell in /etc/passwd File

In this method, simply open the /etc/passwd file using any of your favorite command line text editors and change a specific users shell.

Change User Shell in Passwd File

When your done editing, save and close the file.

Do not forget to read these related topics:

In this article, we described various ways of changing a user’s shell in Linux. To share any thoughts with us, use the comment section below.

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