.\"	$OpenBSD: who.1,v 1.21 2007/05/31 19:20:20 jmc Exp $
.\"	$NetBSD: who.1,v 1.5 1994/12/07 04:28:47 jtc Exp $
.\"
.\" Copyright (c) 1986, 1991, 1993
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.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"    notice, this list of conditions and the following disclaimer.
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.\"    may be used to endorse or promote products derived from this software
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.\"     @(#)who.1	8.2 (Berkeley) 12/30/93
.\"
.Dd $Mdocdate: May 31 2007 $
.Dt WHO 1
.Os
.Sh NAME
.Nm who
.Nd display who is logged in
.Sh SYNOPSIS
.Nm who
.Op Fl HmqTu
.Op Ar file
.Nm who
.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
The options are as follows:
.Bl -tag -width Ds
.It Fl H
Write column headings above the regular output.
.It Fl m
Only print information about the current terminal.
This is the
.Tn POSIX
way of saying
.Nm
.Ar am i .
.It Fl q
(Quick.)
List only the names and the number of users currently logged on.
When this option is used, all other options are ignored.
.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 u
Print the idle time for each user.
.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/utmp .
An alternate
.Ar file
may be specified which is usually
.Pa /var/log/wtmp
(or
.Pa /var/log/wtmp.[0-6]
depending on site policy as
.Pa wtmp
can grow quite large and daily versions may or may not
be kept around after compression by
.Xr ac 8 ) .
The
.Pa wtmp
file contains a record of every login, logout,
crash, shutdown and date change
since
.Pa wtmp
was last truncated or
created.
.El
.Pp
If
.Pa /var/log/wtmp
is being used as the file, the user name may be empty
or one of the special characters
.Ql | ,
.Ql } ,
and
.Ql \&~ .
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/log/wtmp
.It Pa /var/log/wtmp.[0-6]
.El
.Sh SEE ALSO
.Xr last 1 ,
.Xr mesg 1 ,
.Xr users 1 ,
.Xr w 1 ,
.Xr getuid 2 ,
.Xr utmp 5
.Sh STANDARDS
The
.Nm
utility is compliant with the
.St -p1003.1-2004
specification.
.Sh HISTORY
A
.Nm
utility appeared in
.At v3 .