WHO(1) INTERACTIVE UNIX System WHO(1)
NAME
who - who is on the system
SYNOPSIS
who [-uTlHqpdbrtas] [ file ]
who am i
who am I
DESCRIPTION
The who command can list the user's name, terminal line,
login time, elapsed time since activity occurred on the
line, and the process-ID of the command interpreter (shell)
for each current UNIX system user. It examines the
/etc/utmp file at login time to obtain its information. If
file is given, that file [which must be in utmp(4) format]
is examined. Usually, file will be /etc/wtmp, which con-
tains a history of all the logins since the file was last
created.
The who command with the am i or am I option identifies the
invoking user.
The general format for output is:
name [state] line time [idle] [pid] [comment] [exit]
The name, line, and time information is produced by all
options except -q; the state information is produced only by
-T; the idle and pid information is produced only by -u and
-l; and the comment and exit information is produced only by
-a. The information produced for -p, -d, and -r is
explained during the discussion of each option below.
With options, who can list logins, logoffs, reboots, and
changes to the system clock, as well as other processes
spawned by the init process. These options are:
-u This option lists only those users who are currently
logged in. The name is the user's login name. The
line is the name of the line as found in the directory
/dev. The time is the time that the user logged in.
The idle column contains the number of hours and
minutes since activity last occurred on that particu-
lar line. A dot (.) indicates that the terminal has
seen activity in the last minute and is therefore
``current.'' If more than twenty-four hours have
elapsed or the line has not been used since boot time,
the entry is marked old. This field is useful when
trying to determine whether a person is working at the
terminal or not. The pid is the process-ID of the
user's shell. The comment is the comment field
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associated with this line as found in /etc/inittab
[see inittab[4]]. This can contain information about
where the terminal is located, the telephone number of
the dataset, type of terminal if hard-wired, etc.
-T This option is the same as the -s option, except that
the state of the terminal line is printed. The state
describes whether someone else can write to that ter-
minal. A + appears if the terminal is writable by
anyone; a - appears if it is not. root can write to
all lines having a + or a - in the state field. If a
bad line is encountered, a ? is printed.
-l This option lists only those lines on which the system
is waiting for someone to login. The name field is
LOGIN in such cases. Other fields are the same as for
user entries except that the state field does not
exist.
-H This option will print column headings above the regu-
lar output.
-q This is a quick who, displaying only the names and the
number of users currently logged on. When this option
is used, all other options are ignored.
-p This option lists any other process which is currently
active and has been previously spawned by init. The
name field is the name of the program executed by init
as found in /etc/inittab. The state, line, and idle
fields have no meaning. The comment field shows the
id field of the line from /etc/inittab that spawned
this process. See inittab(4).
-d This option displays all processes that have expired
and not been respawned by init. The exit field
appears for dead processes and contains the termina-
tion and exit values [as returned by wait(2)] of the
dead process. This can be useful in determining why a
process terminated.
-b This option indicates the time and date of the last
reboot.
-r This option indicates the current run-level of the
init process. In addition, it produces the process
termination status, process id, and process exit
status [see utmp(4)] under the idle, pid, and comment
headings, respectively.
-t This option indicates the last change to the system
clock [via the date(1) command] by root. See su(1M).
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-a This option processes /etc/utmp or the named file with
all options turned on.
-s This option is the default and lists only the name,
line, and time fields.
Note to the super-user: After a shutdown to the single-user
state, who returns a prompt; the reason is that since
/etc/utmp is updated at login time and there is no login in
single-user state, who cannot report accurately on this
state. who am i, however, returns the correct information.
FILES
/etc/utmp
/etc/wtmp
/etc/inittab
SEE ALSO
date(1), init(1M), login(1), mesg(1), su(1M).
wait(2), inittab(4), utmp(4) in the INTERACTIVE SDS Guide
and Programmer's Reference Manual.
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