How to view all currently logged in users in Linux system

Today we will briefly introduce several methods to list logged-in users in Linux systems.

In a multi-user Linux system, there is sometimes a need to query the users currently logged in to the system. For example, a user needs to be logged out for some reason.

Today we will briefly introduce several methods to list logged-in users in Linux systems.

Among the methods we introduced, almost all commands rely on data existing in the /var or /proc directory. If you know anything about directory structure in Linux, you know that these two directories contain data about the processes running on the system.

1. Use the w command to view the logged-in users in the Linux system

This is the simplest method. Just type a letter command to query the users logged in in the current system.

w

The following is the output of the w command:

$ w
 09:54:54 up 26 min,  3 users,  load average: 0.00, 0.00, 0.00
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    202.91.87.114    09:37   21.00s  0.00s  0.00s -bash
abhi     pts/1    202.91.87.114    09:47    0.00s  0.00s  0.00s w
rohini   pts/2    157.43.53.142    09:48    6:13   0.00s  0.00s -bash

Let’s give a brief explanation of the above output, which will also be covered in other commands.

In the above output, TTY displays the terminal information of the user login, where pts represents the pseudo-terminal slave, that is, logged in through ssh connection.

The following columns display the IP address, login time and idle time of the user's computer respectively.

JCPU is the time spent by all processes connected to the TTY, PCPU is the time spent by the current process running by the user. The WHAT column displays the current process.

2, use the who command to view the logged in user

To query logged-in users, the who command is also a commonly used method, and it is also very simple to use.

who

The output is as follows:

$ who
root     pts/0        Aug  6 09:37 (202.91.87.114)
abhi     pts/1        Aug  6 09:47 (202.91.87.114)
rohini   pts/2        Aug  6 09:48 (157.43.53.142)

3, use users command

The above two methods, w command and who command, will display the detailed information of the currently logged in user (such as terminal, IP address, login time, etc.). Sometimes you may only want the user name (for example, if you want to write a script). After using the w or who command, you need to parse its output, which is additional work. So, is there a way to just get the user's login name? The answer is yes, that is to use the users command. As follows:

$ users
abhi rohini root

4, use finger command

The finger command is not pre-installed in all Linux distributions, so you need to install it manually before using it. For example, in Ubuntu you can use the following command to install:

sudo apt install finger

After the installation is complete, you can directly use the finger command to view the list of users logged in in the current system:

finger

The output is as follows:

$ finger
Login     Name             Tty      Idle  Login Time   Office     Office Phone
abhi      Abhishek         pts/1          Aug  6 09:47 (202.91.87.114)
rohini    Rohini Rachita   pts/2      13  Aug  6 09:48 (157.43.53.142)
root      root            *pts/0          Aug  6 09:37 (202.91.87.114)

Others: Check who logged in to the system after the last restart

The method we introduced above is to query the users who are currently logged in to the system. So is there a way to query who has logged in to the system?

The

last command can display which users have logged into the system since the last restart of the system (including those who are currently logged in and those who have logged out). For logged out users, their login time and logout time are also displayed.

last

The output is as follows:

$ last
rohini   pts/3        157.43.53.142    Tue Aug  6 10:05 - 10:05  (00:00)
rohini   pts/2        157.43.53.142    Tue Aug  6 09:48   still logged in
abhi     pts/1        202.91.87.114    Tue Aug  6 09:47   still logged in
root     pts/0        202.91.87.114    Tue Aug  6 09:37   still logged in
reboot   system boot  4.15.0-52-generi Tue Aug  6 09:28   still running
wtmp begins Tue Aug  6 09:28:43 2022

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