NAME

who - display who is logged in

SYNOPSIS

who [-abdHlmqrstTuv] [file] who am i

DESCRIPTION

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:

-a
Same as --bdlprTtuv.

-b
Time of last system boot.

-d
Print dead processes.

-H
Write column headings above the regular output.

-l
Print system login processes.

-m
Only print information about the current terminal. This is the POSIX way of saying who am i.

-p
Print active processes spawned by init(8).

-q
``Quick mode'': List only the names and the number of users currently logged on. When this option is used, all other options are ignored.

-r
Print the current runlevel. Supported runlevels are:

d (DEATH)
The system has halted.

s (SINGLE_USER)
The system is running in single user mode.

r (RUNCOM)
The system is executing /etc/rc.

t (READ_TTYS)
The system is processing /etc/ttys.

m (MULTI_USER)
The system is running in multi-user mode.

T (CLEAN_TTYS)
The system is in the process of stopping processes associated with terminal devices.

c (CATATONIA)
The system is in the process of shutting down and will not create new processes.

-s
List only the name, line and time fields. This is the default.

-T
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.

-t
Print last system clock change.

-u
Print the idle time for each user, and the associated process ID.

-v
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).

FILES

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

SEE ALSO

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

STANDARDS

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

HISTORY

A who utility appeared in Version 6 AT&T UNIX.