January 17, 2007 WHO 1

### NAME

who - display who is logged in

### SYNOPSIS

who [-abdHlmqrstTuv] [file] who am i

### DESCRIPTION

The who 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.

Available options:

-a
  Same as --bdlprTtuv.

-b
  Time of last system boot.

-d
  Print dead processes.

-H
  Write column headings above the regular output.

-l
  Print system login processes.

-m
  Only print information about the current terminal. This is the POSIX way of saying who am i.

-p
  Print active processes spawned by init(8).

-q
  ``Quick mode'': List only the names and the number of users currently logged on. When this option is used, all other options are ignored.

-r
  Print the current runlevel. Supported runlevels are:

  ```d (````DEATH`)
    The system has halted.

  ```s (````SINGLE_USER`)
    The system is running in single user mode.

  ```r (````RUNCOM`)
    The system is executing ```/etc/rc`.

  ```t (````READ_TTYS`)
    The system is processing ```/etc/ttys`.

  ```m (````MULTI_USER`)
    The system is running in multi-user mode.

  ```T (````CLEAN_TTYS`)
    The system is in the process of stopping processes associated with terminal devices.

  ```c (````CATATONIA`)
    The system is in the process of shutting down and will not create new processes.

-s
  List only the name, line and time fields. This is the default.

-T
  Print a character after the user name indicating the state of the terminal line: `+' if the terminal is writable; `-' if it is not; and `?' if a bad line is encountered.

-t
  Print last system clock change.

-u
  Print the idle time for each user, and the associated process ID.

-v
  When printing of more information is requested with -u, this switch can be used to also printed process termination signals, process exit status, session id for windowing and the type of the entry, see documentation of ut_type in getutxent(3).

am I
  Returns the invoker's real user name.

file
  By default, who gathers information from the file ```/var/run/utmpx`. An alternative file may be specified which is usually ```/var/log/wtmpx` (or ```/var/log/wtmp`, or ```/var/log/wtmpx.[0-6]` or ```/var/log/wtmp.[0-6]` depending on site policy as ```wtmpx` can grow quite large and daily versions may or may not be kept around after compression by ac(8)). The ```wtmpx` and ```wtmp` file contains a record of every login, logout, crash, shutdown and date change since ```wtmpx` and ```wtmp` were last truncated or created.

If ```/var/log/wtmpx` or ```/var/log/wtmp` are 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 utmp(5).

### FILES

```/var/run/utmp`
```/var/run/utmpx`
```/var/log/wtmp`
```/var/log/wtmp.[0-6]`
```/var/log/wtmpx`
```/var/log/wtmpx.[0-6]`

### SEE ALSO

last(1), mesg(1), users(1), getuid(2), utmp(5), utmpx(5)

### STANDARDS

The who utility is expected to conform to IEEE Std 1003.2-1992 (``POSIX.2'') .

### HISTORY

A who utility appeared in Version 6 `AT&T UNIX`.