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Linux 2.6 - man page for who (linux section 1posix)

WHO(P)				    POSIX Programmer's Manual				   WHO(P)

       who - display who is on the system

       who [-mTu]

       who [-mu]-s[-bHlprt][file]

       who [-mTu][-abdHlprt][file]

       who -q [file]

       who am i

       who am I

       The  who  utility  shall  list  various	pieces of information about accessible users. The
       domain of accessibility is implementation-defined.

       Based on the options given, who can also list the user's name, terminal line, login  time,
       elapsed time since activity occurred on the line, and the process ID of the command inter-
       preter for each current system user.

       The who utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Sec-
       tion 12.2, Utility Syntax Guidelines.

       The  following  options	shall  be  supported. The metavariables, such as <line>, refer to
       fields described in the STDOUT section.

       -a     Process the implementation-defined database or named file with the -b, -d, -l,  -p,
	      -r, -t, -T and -u options turned on.

       -b     Write the time and date of the last reboot.

       -d     Write  a list of all processes that have expired and not been respawned by the init
	      system process. The <exit> field shall appear for dead processes	and  contain  the
	      termination  and exit values of the dead process. This can be useful in determining
	      why a process terminated.

       -H     Write column headings above the regular output.

       -l     (The letter ell.) List only those lines on which the system is waiting for  someone
	      to  login. The <name> field shall be LOGIN in such cases. Other fields shall be the
	      same as for user entries except that the <state> field does not exist.

       -m     Output only information about the current terminal.

       -p     List any other process that is currently active and has been previously spawned  by

       -q     (Quick.) List only the names and the number of users currently logged on. When this
	      option is used, all other options shall be ignored.

       -r     Write the current run-level of the init process.

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

       -t     Indicate the last change to the system clock.

       -T     Show the state of each terminal, as described in the STDOUT section.

       -u     Write "idle time" for each displayed user in addition to any other information. The
	      idle  time  is  the  time  since	any activity occurred on the user's terminal. The
	      method of determining this is unspecified.    This option  shall	list  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 <activity> is the number of hours and minutes since activ-
	      ity last occurred on that particular 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
	      shall be marked <old>. This field is useful when trying to determine whether a per-
	      son is working at the terminal or not. The <pid> is the process ID  of  the  user's
	      login process.

       The following operands shall be supported:

       am i, am I
	      In  the  POSIX locale, limit the output to describing the invoking user, equivalent
	      to the -m option. The am and i or I must be separate arguments.

       file   Specify a pathname of a file to substitute for the implementation-defined  database
	      of logged-on users that who uses by default.

       Not used.


       The following environment variables shall affect the execution of who:

       LANG   Provide  a  default  value for the internationalization variables that are unset or
	      null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Inter-
	      nationalization Variables for the precedence of internationalization variables used
	      to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the  other  interna-
	      tionalization variables.

	      Determine  the  locale for the interpretation of sequences of bytes of text data as
	      characters (for example, single-byte as opposed to multi-byte characters	in  argu-

	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error.

	      Determine the locale used for the format and contents of the date and time strings.

	      Determine the location of message catalogs for the processing of LC_MESSAGES .

       TZ     Determine the timezone used when writing date and time information.  If TZ is unset
	      or null, an unspecified default timezone shall be used.


       The  who  utility  shall write its default format to the standard output in an implementa-
       tion-defined format, subject  only  to  the  requirement  of  containing  the  information
       described above.

       XSI-conformant  systems	shall write the default information to the standard output in the
       following general format:


       The following format shall be used for the -T option:

	      "%s %c %s %s\n" <name>, <terminal state>, <terminal name>,
		  <time of login>

       where <terminal state> is one of the following characters:

       +      The terminal allows write access to other users.

       -      The terminal denies write access to other users.

       ?      The terminal write-access state cannot be determined.

       In the POSIX locale, the <time of login> shall be equivalent in format to the output of:

	      date +"%b %e %H:%M"

       If the -u option is used with -T, the idle time shall be added to the end of the  previous
       format in an unspecified format.

       The standard error shall be used only for diagnostic messages.



       The following exit values shall be returned:

	0     Successful completion.

       >0     An error occurred.


       The following sections are informative.

       The name init used for the system process is the most commonly used on historical systems,
       but it may vary.

       The "domain of accessibility" referred to is a broad concept that  permits  interpretation
       either on a very secure basis or even to allow a network-wide implementation like the his-
       torical rwho.


       Due to differences between historical implementations, the base options	provided  were	a
       compromise  to allow users to work with those functions. The standard developers also con-
       sidered removing all the options, but felt that these options offered users valuable func-
       tionality.  Additional options to match historical systems are available on XSI-conformant

       It is recognized that the who command may be of limited usefulness, especially in a multi-
       level  secure  environment.  The standard developers considered, however, that having some
       standard method of determining the "accessibility" of other users would aid user portabil-

       No  format  was	specified  for	the default who output for systems not supporting the XSI
       Extension. In such a user-oriented command, designed only for human use, this was not con-
       sidered to be a deficiency.

       The  format  of	the  terminal  name is unspecified, but the descriptions of ps, talk, and
       write require that they use the same format.

       It is acceptable for an implementation to produce no output for an invocation of who mil.



       Portions of this text are reprinted and	reproduced  in	electronic  form  from	IEEE  Std
       1003.1,	2003  Edition,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  by
       the  Institute  of  Electrical  and  Electronics Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					   WHO(P)

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