who.1

早期freebsd实现

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.\"     @(#)who.1	8.2 (Berkeley) 12/30/93
.\"
.Dd December 30, 1993
.Dt WHO 1
.Os
.Sh NAME
.Nm who
.Nd display who is logged in
.Sh SYNOPSIS
.Nm who
.Op Ar am I
.Op Ar file 
.Sh DESCRIPTION
The utility
.Nm who
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:
.Pp
.Bl -tag -width file
.It Ar \&am I
Returns the invoker's real user name. 
.It Ar file
By default,
.Nm who
gathers information from the file
.Pa /var/run/utmp .
An alternate
.Ar file
may be specified which is usually
.Pa /var/run/wtmp
(or
.Pa /var/run/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 '|', '}' 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/log/wtmp
.It Pa /var/log/wtmp.[0-6]
.El
.Sh SEE ALSO
.Xr last 1 ,
.Xr users 1 ,
.Xr getuid 2 ,
.Xr utmp 5
.Sh HISTORY
A
.Nm
command appeared in
.At v6 .