The who command

The who command lets you print out a list of logged-in users, the current run level of the system and the time of last system boot.

Examples

• Print out all details of currently logged-in users

[root@academy ~]# who -a
           system boot  2023-12-23 15:22
LOGIN      tty1         2023-12-23 15:22               663 id=tty1
           run-level 3  2023-12-23 15:22
root     + pts/0        2023-12-23 15:25   .          1732 (192.168.73.1)
apa      + pts/1        2023-12-23 16:42 00:03       14680 (192.168.73.1)
[root@academy ~]#

• Print out the list of all dead processes

[root@academy ~]# who -d -H
NAME     LINE         TIME             IDLE          PID COMMENT  EXIT
         pts/1        2023-12-23 16:47             14680 id=ts/1  term=0 exit=0

Syntax:

who [options] [filename]

Additional Flags and their Functionalities

Short Flag	Description
-r	prints all the current runlevel
-d	print all the dead processes
-q	print all the login names and total number of logged on users
-h	print the heading of the columns displayed
-b	print the time of last system boot

[root@academy ~]# who -r
         run-level 3  2023-12-23 15:22
[root@academy ~]# who -d
         pts/1        2023-12-23 16:47             14680 id=ts/1  term=0 exit=0
[root@academy ~]# who -q
root
# users=1
[root@academy ~]# who -b
         system boot  2023-12-23 15:22
[root@academy ~]#