NAME
     who - display who is logged in

SYNOPSIS
     who [am I] [file]

DESCRIPTION
     The utility 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.

     Available options:

     am I  Returns the invoker's real user name.

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

     If /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 out-
     put line without any user name.  For more information on the special
     characters, see utmp(5).

FILES
     /var/run/utmp
     /var/log/wtmp
     /var/log/wtmp.[0-6]

SEE ALSO
     last(1),  users(1),  getuid(2),  utmp(5)

HISTORY
     A who command appeared in Version 6 AT&T UNIX.