who(1) [opendarwin man page]

WHO(1)							    BSD General Commands Manual 						    WHO(1)

NAME

     who -- display who is on the system

SYNOPSIS

     who [-HmqsTu] [am I] [file]

DESCRIPTION

     The who utility displays information about currently logged in users.  By default, this includes the login name, tty name, date and time of
     login and remote hostname if not local.

     The options are as follows:

     -H      Write column headings above the output.

     -m      Show information about the terminal attached to standard input only.

     -q      ``Quick mode'': List the names and number of logged in users in columns.  All other command line options are ignored.

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

     -T      Indicate whether each user is accepting messages.	One of the following characters is written:

	     +	User is accepting messages.
	     -	User is not accepting messages.
	     ?	An error occurred.

     -u      Show idle time for each user in hours and minutes as hh:mm, '.' if the user has been idle less that a minute, and ``old'' if the user
	     has been idle more than 24 hours.

     am I    Equivalent to -m.

     By default, who gathers information from the file /var/run/utmp.  An alternate file may be specified which is usually /var/log/wtmp (or
     /var/log/wtmp.[0-6] depending on site policy as wtmp can grow quite large and daily versions may or may not be kept around after compression
     by ac(8)).  The wtmp file contains a record of every login, 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
     output line without any user name.  For more information on the special characters, see utmp(5).

ENVIRONMENT

     The COLUMNS, LANG, LC_ALL and LC_TIME environment variables affect the execution of who as described in environ(7).

FILES

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

DIAGNOSTICS

     The who utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

     last(1), users(1), w(1), utmp(5)

STANDARDS

     The who utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

HISTORY

     A who command appeared in Version 1 AT&T UNIX.

BSD
								    May 8, 2002 							       BSD

UTMP(5) 						      BSD File Formats Manual							   UTMP(5)

NAME

     utmp, wtmp, lastlog -- login records (DEPRECATED)

SYNOPSIS

     #include <utmp.h>

DESCRIPTION

     The interfaces in file <utmp.h> are all DEPRECATED and are only provided for compatibility with previous releases of Mac OS X.  See
     pututxline(3) and utmpx(5) for the supported interfaces.

     <utmp.h> declares the structures used to record information about current users in the file utmp, logins and logouts in the file wtmp, and
     last logins in the file lastlog.  The time stamps of date changes, shutdowns and reboots are also logged in the wtmp file.

     These files can grow rapidly on busy systems, daily or weekly rotation is recommended.  If any of these files do not exist, it is not cre-
     ated.  These files must be created manually and are normally maintained in either the script /etc/daily or the script /etc/weekly.  (See
     cron(8).)

	   #define _PATH_UTMP	   "/var/run/utmp"
	   #define _PATH_WTMP	   "/var/log/wtmp"
	   #define _PATH_LASTLOG   "/var/log/lastlog"

	   #define UT_NAMESIZE	   8
	   #define UT_LINESIZE	   8
	   #define UT_HOSTSIZE	   16

	   struct lastlog {
		   time_t  ll_time;
		   char    ll_line[UT_LINESIZE];
		   char    ll_host[UT_HOSTSIZE];
	   };

	   struct utmp {
		   char    ut_line[UT_LINESIZE];
		   char    ut_name[UT_NAMESIZE];
		   char    ut_host[UT_HOSTSIZE];
		   time_t  ut_time;
	   };

     Each time a user logs in, the login program looks up the user's UID in the file lastlog. If it is found, the timestamp of the last time the
     user logged in, the terminal line and the hostname are written to the standard output. (Providing the login is not quiet, see login(1).)  The
     login program then records the new login time in the file lastlog.

     After the new lastlog record is written , the file utmp is opened and the utmp record for the user inserted.  This record remains there until
     the user logs out at which time it is deleted.  The utmp file is used by the programs rwho(1), users(1), w(1), and who(1).

     Next, the login program opens the file wtmp, and appends the user's utmp record.  The same utmp record, with an updated time stamp is later
     appended to the file when the user logs out. (See launchd(8).)  The wtmp file is used by the programs last(1) and ac(8).

     In the event of a date change, a shutdown or reboot, the following items are logged in the wtmp file.

     reboot
     shutdown	 A system reboot or shutdown has been initiated.  The character '~' is placed in the field ut_line, and reboot or shutdown in the
		 field ut_name.  (See shutdown(8) and reboot(8).)

     date	 The system time has been manually or automatically updated.  (See date(1).)  The command name date is recorded in the field
		 ut_name.  In the field ut_line, the character '|' indicates the time prior to the change, and the character '{' indicates the new
		 time.

FILES

     (These files no longer exist in 10.5 or later.)

     /var/run/utmp     The utmp file.
     /var/log/wtmp     The wtmp file.
     /var/log/lastlog  The lastlog file.

SEE ALSO

     last(1), login(1), who(1), ac(8), launchd(8)

HISTORY

     A utmp and wtmp file format appeared in Version 6 AT&T UNIX.  The lastlog file format appeared in 3.0BSD.

4th Berkeley Distribution					  March 17, 1994					 4th Berkeley Distribution