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WHO(1P)                    POSIX Programmer's Manual                   WHO(1P)

       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

       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

       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 interpreter for each current system user.

       The  who  utility  shall  conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 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 init.

       -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 activity 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 person is work-
              ing 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, Internationalization Variables for  the  prece-
              dence 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 internationalization variables.

              Determine the locale for the interpretation of sequences of bytes of text data as characters (for  exam-
              ple, single-byte as opposed to multi-byte characters in arguments).

              Determine  the locale that should be used to affect the format and contents of diagnostic messages writ-
              ten 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 unspeci-
              fied default timezone shall be used.


       The who utility shall write its default format to the standard output in an implementation-defined format, sub-
       ject 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 for-


       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 unspeci-
       fied 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 historical 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 considered removing all the options, but  felt
       that  these  options  offered  users valuable functionality. Additional options to match historical systems are
       available on XSI-conformant systems.

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

       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 considered 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, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, the original IEEE and The Open Group Standard is the referee  document.  The  original  Standard  can  be
       obtained online at .

IEEE/The Open Group                  2003                              WHO(1P)