who(1p) — Linux manual page


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

PROLOG         top

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

NAME         top

       who — display who is on the system

SYNOPSIS         top

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

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

       who -q [file]

       who am i

       who am I

DESCRIPTION         top

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

       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.

OPTIONS         top

       The who utility shall conform to the Base Definitions volume of
       POSIX.1‐2017, 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 system reboot. The
                 system reboot time is the time at which the
                 implementation is able to commence running processes.

       -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 working at the terminal or not. The <pid> is
                 the process ID of the user's login process.

OPERANDS         top

       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.

STDIN         top

       Not used.

INPUT FILES         top



       The following environment variables shall affect the execution of

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base
                 Definitions volume of POSIX.1‐2017, Section 8.2,
                 Internationalization 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 internationalization variables.

       LC_CTYPE  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 arguments).

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

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

       NLSPATH   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.



STDOUT         top

       The who utility shall write its default format to the standard
       output in an implementation-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:


       For the -b option, <line> shall be "systemboot".  The <name> is

       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.

       <space> This entry is not associated with a terminal.

       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.

STDERR         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top




EXIT STATUS         top

       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.

EXAMPLES         top


RATIONALE         top

       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 environment. The
       standard developers considered, however, that having some
       standard method of determining the ``accessibility'' of other
       users would aid user portability.

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

       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.



SEE ALSO         top


       The Base Definitions volume of POSIX.1‐2017, Chapter 8,
       Environment Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                           WHO(1P)

Pages that refer to this page: id(1p)logname(1p)talk(1p)write(1p)