who(1) CLIX who(1)
NAME
who - Lists users logged onto the system
SYNOPSIS
who [-uTlHqnpdbrtasA] [file]
who am i
who am I
FLAGS
-A Lists accounting information associated with login usage. To use
this flag, system accounting software must be enabled and the command
must be invoked with the following string:
who -A /etc/wtmp
When using this string, the system will look for accounting
information in the /etc/wtmp file.
-a Processes the /etc/utmp file or a named file with all flags turned
on.
-b Indicates the time and date of the last reboot.
-d Displays all processes that have expired and have not been respawned
by init. The exit field appears for dead processes and contains the
termination and exit values (as returned by the wait() function) of
the dead process. This can be useful in determining why a process
terminated.
-H Displays column headings above the regular output.
-l Lists only those lines on which the system is waiting for someone to
log in. In such cases, the name in the name field is LOGIN. Other
fields are the same as for user entries, except that the state field
does not exist.
-n Specifies the number of users per line; used only with the -q flag.
Following the -n flag, the user must specify the number of columns
the output should have.
-p Lists any other process currently active and previously spawned by
init. The name field contains the name of the program executed by
init as found in /etc/inittab. The state, line, and idle time fields
have no meaning. The comment field shows the ID field of the line
from /etc/inittab that spawned this process.
2/94 - Intergraph Corporation 1
who(1) CLIX who(1)
-q Displays a quick version of who, displaying only the names and the
number of users currently logged on. When this flag is specified,
all other flags are ignored.
-r 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) in the idle time, PID, and comment fields,
respectively.
-s Lists the default options (the name, line, and time fields).
-T Lists the state of the terminal line in addition to the name, line,
and time fields. The state describes whether someone else can write
to that terminal. A plus sign (+) appears if the terminal is
writable by anyone; a dash (-) appears if it is not. The root
directory can write to all lines having a plus sign or a dash in the
state field. If a bad line is encountered, a question mark (?) is
displayed.
-t Indicates the last change to the system clock (with the date command)
by root. (See su.)
-u Lists only those users currently logged on. The output displayed by
who -u contains the following fields:
Name Lists the user's login name.
Line Lists the name of the line as found in /dev.
Time Lists the time the user logged in to the system.
Idle time
Lists the number of hours and minutes since activity last
occurred on the user's line. A dot (.) indicates that the
terminal has seen activity within the last minute and is
therefore ``current.'' If more than 24 hours have elapsed or
the line has not been used since system boot, the entry is
marked old. This field is useful when trying to determine
whether a user is working at a terminal.
Process ID (PID)
Lists the process ID of the user's shell.
Comments
Lists the comment associated with the user's line as found in
/etc/inittab. This field can contain information concerning
the terminal's location, the telephone number of the dataset,
the type of terminal if hard-wired, and so on.
If a user logs in from a remote system using telnet or rlogin, the
host name is listed in the last column of the displayed output.
2 Intergraph Corporation - 2/94
who(1) CLIX who(1)
DESCRIPTION
The who command lists 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 UNIX system user currently logged on.
The command examines the /etc/utmp file at login time to obtain the
information it lists. If a file is specified, that file, which must be in
utmp format (see utmp(4)), is examined. Usually, the specified file will
be /etc/wtmp, which contains a history of all the logins since the file
was last created.
When the who command is used along with am i or am I, the system
identifies the invoking user.
The general format for output of the who command is as follows:
name [state] line time [idle] [pid] [comments] [exit]
The name, line, and time information is produced by all flags 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 the -p, -d, and -r
system output flags are explained in the FLAGS section of this document.
EXAMPLES
1. The following displays the invoking user's username, terminal, and
login time:
who am i
2. The following displays the processes waiting for a login and terminal
state information; column headers are also displayed:
who -TlH
3. The following lists only the usernames and the number of users:
who -q
4. The following displays information about the current level:
who -r
5. The following tells when the system was last booted:
who -b
2/94 - Intergraph Corporation 3
who(1) CLIX who(1)
6. The following lists a quick version of the who command with output
appearing in four columns:
who -qn4
FILES
/etc/wtmp
/etc/utmp
User and accounting information.
/etc/utmp2
Information on users logged in from remote hosts.
/etc/inittab
Script for the init process.
NOTES
After a shutdown while in the single-user state, the who command returns
to the prompt because the /etc/utmp file is updated only at login time and
there is no login in the single-user state. Thus, the who command cannot
accurately report on this state. However, the who am i, command returns
the correct information.
When using the who -A command to access accounting information, the system
accounting software database must be loaded and the filenames or
information should be included in the /etc/wtmp file.
DIAGNOSTICS
In order for the who am I diagnostic messages to be displayed, the user
login must first be associated with a terminal. When using the who am i
command, there must be a controlling terminal when the command is issued.
EXIT VALUES
The who command exits with a 0 if successful, or with a nonzero value if
an error occurs.
RELATED INFORMATION
Commands: date(1), login(1), mesg(1), su(1), init(1)
Functions: wait(2)
Files: inittab(4), utmp(4)
4 Intergraph Corporation - 2/94