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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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 differ (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] [−abdHlprt] [file]
who [−mu] −s [−bHlprt] [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 interpreter for each
current system user.
The who utility shall conform to the Base Definitions volume of
POSIX.1‐2008, 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.
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.
None.
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 POSIX.1‐2008, 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).
LC_MESSAGES
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.
Default.
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:
<name>[<state>]<line><time>[<activity>][<pid>][<comment>][<exit>]
For the −b option, <line> shall be "systemboot". The <name> is
unspecified.
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.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
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.
None.
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 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.
None.
mesg(1p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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 2013 WHO(1P)
Pages that refer to this page: id(1p), logname(1p), talk(1p), write(1p)