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.\"     @(#)who.1	8.2 (Berkeley) 12/30/93
.\"
.Dd September 1, 2019
.Dt WHO 1
.Os
.Sh NAME
.Nm who
.Nd display who is logged in
.Sh SYNOPSIS
.Nm
.Op Fl abdHlmqrsTtuv
.Op Ar file
.Nm
.Ar am i
.Sh DESCRIPTION
The
.Nm
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.
.Pp
Available options:
.Bl -tag -width file
.It Fl a
Same as
.Fl -bdlprTtuv .
.It Fl b
Time of last system boot.
.It Fl d
Print dead processes.
.It Fl H
Write column headings above the regular output.
.It Fl l
Print system login processes.
.It Fl m
Only print information about the current terminal.
This is the POSIX way of saying
.Nm
.Ar am i .
.It Fl p
Print active processes spawned by
.Xr init 8 .
.It Fl q
.Dq Quick mode :
List only the names and the number of users currently logged on.
When this option is used, all other options are ignored.
.It Fl r
Print the current runlevel.
Supported runlevels are:
.Bl -tag -width "s (SINGLE_USER)"
.It Dv d Pq Dv DEATH
The system has halted.
.It Dv s Pq Dv SINGLE_USER
The system is running in single user mode.
.It Dv r Pq Dv RUNCOM
The system is executing
.Pa /etc/rc .
.It Dv t Pq Dv READ_TTYS
The system is processing
.Pa /etc/ttys .
.It Dv m Pq Dv MULTI_USER
The system is running in multi-user mode.
.It Dv T Pq Dv CLEAN_TTYS
The system is in the process of stopping processes
associated with terminal devices.
.It Dv c Pq Dv CATATONIA
The system is in the process of shutting down and will
not create new processes.
.El
.It Fl s
List only the name, line and time fields.
This is the default.
.It Fl T
Print a character after the user name indicating the state of the
terminal line:
.Sq +
if the terminal is writable;
.Sq -
if it is not;
and
.Sq \&?
if a bad line is encountered.
.It Fl t
Print last system clock change.
.It Fl u
Print the idle time for each user, and the associated process ID.
.It Fl v
When printing of more information is requested with
.Fl 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
.Xr getutxent 3 .
.It Ar \&am I
Returns the invoker's real user name.
.It Ar file
By default,
.Nm
gathers information from the file
.Pa /var/run/utmpx .
An alternative
.Ar file
may be specified which is usually
.Pa /var/log/wtmpx
(or
.Pa /var/log/wtmp ,
or
.Pa /var/log/wtmpx.[0-6]
or
.Pa /var/log/wtmp.[0-6]
depending on site policy as
.Pa wtmpx
can grow quite large and daily versions may or may not
be kept around after compression by
.Xr ac 8 ) .
The
.Pa wtmpx
and
.Pa wtmp
file contains a record of every login, logout,
crash, shutdown and date change
since
.Pa wtmpx
and
.Pa wtmp
were last truncated or
created.
.El
.Pp
If
.Pa /var/log/wtmpx
or
.Pa /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
.Xr utmp 5 .
.Sh FILES
.Bl -tag -width /var/log/wtmp.[0-6] -compact
.It Pa /var/run/utmp
.It Pa /var/run/utmpx
.It Pa /var/log/wtmp
.It Pa /var/log/wtmp.[0-6]
.It Pa /var/log/wtmpx
.It Pa /var/log/wtmpx.[0-6]
.El
.Sh SEE ALSO
.Xr last 1 ,
.Xr mesg 1 ,
.Xr users 1 ,
.Xr getuid 2 ,
.Xr utmp 5 ,
.Xr utmpx 5
.Sh STANDARDS
The
.Nm
utility is expected to conform to
.St -p1003.2-92 .
.Sh HISTORY
A
.Nm
utility appeared in
.At v1 :
.Lk https://www.bell-labs.com/usr/dmr/www/man14.pdf