WHO(1) General Commands Manual WHO(1)

who — display who is logged in

who [-abdHlmqrsTtuv] [file]

who am i

The who utility displays a list of all users currently logged on, showing for each user the login name, tty name, the date and time of login, and hostname if not local.

Available options:

Same as -bdlprTtuv.
Time of last system boot.
Print dead processes.
Write column headings above the regular output.
Print system login processes.
Only print information about the current terminal. This is the POSIX way of saying who am i.
Print active processes spawned by init(8).
“Quick mode”: List only the names and the number of users currently logged on. When this option is used, all other options are ignored.
Print the current runlevel. Supported runlevels are:
(DEATH)
The system has halted.
(SINGLE_USER)
The system is running in single user mode.
(RUNCOM)
The system is executing /etc/rc.
(READ_TTYS)
The system is processing /etc/ttys.
(MULTI_USER)
The system is running in multi-user mode.
(CLEAN_TTYS)
The system is in the process of stopping processes associated with terminal devices.
(CATATONIA)
The system is in the process of shutting down and will not create new processes.
List only the name, line and time fields. This is the default.
Print a character after the user name indicating the state of the terminal line: ‘+’ if the terminal is writable; ‘-’ if it is not; and ‘?’ if a bad line is encountered.
Print last system clock change.
Print the idle time for each user, and the associated process ID.
When printing of more information is requested with -u, this switch can be used to also printed process termination signals, process exit status, session id for windowing and the type of the entry, see documentation of ut_type in getutxent(3).
am I
Returns the invoker's real user name.
file
By default, who gathers information from the file /var/run/utmpx. An alternative file may be specified which is usually /var/log/wtmpx (or /var/log/wtmp, or /var/log/wtmpx.[0-6] or /var/log/wtmp.[0-6] depending on site policy as wtmpx can grow quite large and daily versions may or may not be kept around after compression by ac(8)). The wtmpx and wtmp file contains a record of every login, logout, crash, shutdown and date change since wtmpx and wtmp were last truncated or created.

If /var/log/wtmpx or /var/log/wtmp are being used as the file, the user name may be empty or one of the special characters '|', '}' and '~'. Logouts produce an output line without any user name. For more information on the special characters, see utmp(5).

/var/run/utmp
 
/var/run/utmpx
 
/var/log/wtmp
 
/var/log/wtmp.[0-6]
 
/var/log/wtmpx
 
/var/log/wtmpx.[0-6]
 

last(1), mesg(1), users(1), getuid(2), utmp(5), utmpx(5)

The who utility is expected to conform to IEEE Std 1003.2-1992 (“POSIX.2”).

A who utility appeared in Version 1 AT&T UNIX: https://www.bell-labs.com/usr/dmr/www/man14.pdf

September 1, 2019 NetBSD 11.0