who
Show who is logged on
TLDR
Display the username, line, and time of all currently logged-in sessions
Display all available information
Display all available information with table headers
SYNOPSIS
who [OPTION]... [FILE] [am i]
PARAMETERS
-a, --all
Equivalent to -b -d --login -p -r -t -T -u
-b, --boot
Time of last system boot
-d, --dead
List dead processes
-H, --heading
Print column headers
-i, --idle
Add idle time in hours and minutes
-l, --login
List system login processes
-m
Only hostname and user associated with stdin
-n, --count=N
List at most N users
-p, --process
List active processes spawned by init
-q, --count
List all login names and the number of users logged on
-r, --runlevel
Current runlevel
-s, --short
List only name, line, and time
-t, --time
Show last system clock change
-T, -w, --mesg
Add message status as +, - or ?
-u, --users
List users logged in
--message-format=FORMAT
Use FORMAT when reporting user's message status
--version
Output version information and exit
--help
Display this help and exit
am i
Equivalent to 'who am i'
DESCRIPTION
The who command is a fundamental utility that provides information about users currently logged into the system. It displays details such as the user's login name, terminal line, login time, and the remote host if applicable.
Who is invaluable for system administrators and users alike who need to monitor system activity and determine who is actively using the system's resources. The command can also provide information about system boot time, runlevel, and other system-related events.
Its versatility is further enhanced by numerous options, allowing for tailored output to meet specific needs, from a simple list of users to a more detailed report on system events.
FILE ARGUMENT
If FILE is specified, who uses that file instead of /var/run/utmp or /var/log/wtmp. Given as an argument, the am i option finds the corresponding entry in the file.
HISTORY
The who command is one of the oldest utilities in Unix-like operating systems. It has been present since the earliest versions of Unix and has remained a core part of the system administration toolkit.
Originally, it provided a simple way to determine who was logged into the system, which was essential for communication and resource management in multi-user environments. Over time, the command has evolved with the addition of various options to provide more detailed system information.