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.Dd August 30, 2020
.Dt WHO 1
.Os
.Sh NAME
.Nm who
.Nd display who is on the system
.Sh SYNOPSIS
.Nm
.Op Fl abHmqsTu
.Op Cm am I
.Op Ar file
.Sh DESCRIPTION
The
.Nm
utility displays information about currently logged in users.
By default, this includes the login name, tty name, date and time of login and
remote hostname if not local.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl a
Equivalent to
.Fl bTu ,
with the exception that output is not restricted to the time and date of
the last system reboot.
.It Fl b
Write the time and date of the last system reboot.
.It Fl H
Write column headings above the output.
.It Fl m
Show information about the terminal attached to standard input only.
.It Fl q
.Dq "Quick mode" :
List the names and number of logged in users in columns.
All other command line options are ignored.
.It Fl s
Show the name, line and time fields only.
This is the default.
.It Fl T
Indicate whether each user is accepting messages.
One of the following characters is written:
.Pp
.Bl -tag -width 1n -compact
.It Li +
User is accepting messages.
.It Li \&-
User is not accepting messages.
.It Li \&?
An error occurred.
.El
.It Fl u
Show idle time for each user in hours and minutes as
.Ar hh : Ns Ar mm ,
.Ql \&.
if the user has been idle less than a minute, and
.Dq Li old
if the user has been idle more than 24 hours.
.It Cm am I
Equivalent to
.Fl m .
.El
.Pp
By default,
.Nm
gathers information from the file
.Pa /var/run/utx.active .
An alternate
.Ar file
may be specified which is usually
.Pa /var/log/utx.log
(or
.Pa /var/log/utx.log.[0-6]
depending on site policy as
.Pa utx.log
can grow quite large and daily versions may or may not
be kept around after compression by
.Xr ac 8 ) .
The
.Pa utx.log
file contains a record of every login, logout,
crash, shutdown and date change
since
.Pa utx.log
was last truncated or
created.
.Pp
If
.Pa /var/log/utx.log
is 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 getutxent 3 .
.Sh ENVIRONMENT
The
.Ev COLUMNS , LANG , LC_ALL
and
.Ev LC_TIME
environment variables affect the execution of
.Nm
as described in
.Xr environ 7 .
.Sh FILES
.Bl -tag -width /var/log/utx.log.[0-6] -compact
.It Pa /var/run/utx.active
.It Pa /var/log/utx.log
.It Pa /var/log/utx.log.[0-6]
.El
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
Show a brief summary of who is logged in:
.Bd -literal -offset indent
$ who -q
fernape          root             root
# users = 3
.Ed
.Pp
Show who is logged in along with the line and time fields (without the headers):
.Bd -literal -offset indent
$ who -s
fernape          ttyv0        Aug 26 16:23
root             ttyv1        Aug 26 16:23
root             ttyv2        Aug 26 16:23
.Ed
.Pp
Show information about the terminal attached to standard input:
.Bd -literal -offset indent
$ who am i
fernape                       Aug 26 16:24
.Ed
.Pp
Show time and date of the last system reboot, whether the users accept messages
and the idle time for each of them:
.Bd -literal -offset indent
$ who -a
                 - system boot  Aug 26 16:23   .
fernape          - ttyv0        Aug 26 16:23   .
root             - ttyv1        Aug 26 16:23   .
root             - ttyv2        Aug 26 16:23   .
.Ed
.Pp
Same as above but showing headers:
.Bd -literal -offset indent
$ who -aH
NAME             S LINE         TIME         IDLE  FROM
                 - system boot  Aug 26 16:23   .
fernape          - ttyv0        Aug 26 16:23   .
root             - ttyv1        Aug 26 16:23 00:01
root             - ttyv2        Aug 26 16:23 00:01
.Ed
.Sh SEE ALSO
.Xr last 1 ,
.Xr users 1 ,
.Xr w 1 ,
.Xr getutxent 3
.Sh STANDARDS
The
.Nm
utility conforms to
.St -p1003.1-2001 .
.Sh HISTORY
A
.Nm
command appeared in
.At v1 .