w command is used to show logged-in user names and what they are doing. The information will be read from /var/run/utmp file. The output of the w command contains the following columns:

Name of the user
User’s machine number or tty number
Remote machine address
User’s Login time
Idle time (not usable time)
Time used by all processes attached to the tty (JCPU time)
Time used by the current process (PCPU time)
Command currently getting executed by the users

Following options can be used for the w command:

-h Ignore the header information
-u Display the load average (uptime output)
-s Remove the JCPU, PCPU, and login time.

[root@austin ~]# w
 15:46:21 up 23 days, 1 min,  1 user,  load average: 0.00, 0.00, 0.00
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    66.226.xx.x    15:46    0.00s  0.06s  0.00s w

[root@austin ~]# w -h
root     pts/0    66.226.79.7      15:46    0.00s  0.06s  0.00s w -h

[root@austin ~]# w -u
 15:47:05 up 23 days, 2 min,  1 user,  load average: 0.00, 0.00, 0.00
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    66.226.79.7      15:46    0.00s  0.06s  0.00s w -u

[root@austin ~]# w -s
 15:47:23 up 23 days, 2 min,  1 user,  load average: 0.00, 0.00, 0.00
USER     TTY      FROM               IDLE WHAT
root     pts/0    66.226.79.7       0.00s w -s

2. Get the user name and process of logged in user using who and users command

who command is used to get the list of the usernames who are currently logged in. Output of the who command contains the following columns: user name, tty number, date and time, machine address.

[root@austin ~]# who
root     pts/0        2014-07-11 15:46 (66.226.79.7)

To get a list of all usernames that are currently logged in, use the following:

[root@austin ~]# who | cut -d' ' -f1 | sort | uniq
root

Users Command

users command is used to print the user name who are all currently logged in the current host. It is one of the command don’t have any option other than help and version. If the user using, ‘n’ number of terminals, the user name will shown in ‘n’ number of time in the output.

[root@austin ~]# users
root

3. Get the username you are currently logged in using whoami. whoami command is used to print the loggedin user name.

[root@austin ~]# whoami
root

whoami command gives the same output as id -un as shown below:

[root@austin ~]# id -un
root

who am i command will display the logged-in user name and current tty details. The output of this command contains the following columns: logged-in user name, tty name, current time with date and ip-address from where this users initiated the connection.

[root@austin ~]# who am i
root     pts/0        2014-07-11 15:46 (66.226.79.7)

[root@austin ~]# who mom likes
root     pts/0        2014-07-11 15:46 (66.226.79.7)

Warning: Don’t try “who mom hates” command.

Also, if you do su to some other user, this command will give the information about the logged in user name details.

4. Get the user login history at any time

last command will give login history for a specific username. If we don’t give any argument for this command, it will list login history for all users. By default this information will read from /var/log/wtmp file. The output of this command contains the following columns:

User name
Tty device number
Login date and time
Logout time
Total working time

[root@austin ~]# last
root     pts/0        10.1.xx.x    Sat Aug  3 06:49 - down   (00:01)